SCIENCE SCIENCE FOR FOR SOUTH SOUTH AFRICA AFRICA
ISSN 1729-830X ISSN 1729-830X
VOLUME 4 • NUMBER 3 • 2008 VOLUME 3 • NUMBER 2 • 2007 R29.95 R20
Wonder werk C ave and Africa’s pa st
Inve st ing in se e d s Foo d for hea lt h Get t ing a hea d wit h mat h s C hild la b our
A C AACDAEDMEYM YO FO FS C I EI ENNCCEE OOFF SS O U TT HH AAFFRRI C I CA A SC OU
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Discovering the deep African past at Wonderwerk Cave Peter Beaumont and John Vogel Archaeological dating points to the birth of human technology and culture right here in southern Africa 8
Storing and restoring plant-life from seeds Pat Berjak How to store genetic material once considered unstorable
Nutrition – you are what you eat Diet and lifestyle for good health From molecules to society, Esté Vorster (p. 14) • Micronutrients for healthy living, Johann C. Jerling (p. 16) • Eating and exercise, Hattie Wright and Salome Kruger (p. 18) • How blood clots form and disintegrate, Marlien Pieters (p. 20) • Treating children with HIV/AIDS, Salome Kruger (p. 22)
VOLUME 4 • NUMBER 3 • 2008
Sue Nicolson A taste for sugary nectars
Careers: Why maths counts Opening the door to a future in science, technology, and engineering
The struggle continues
Kobus Maree Girls doing science (maths is the key)
Conditioning, Kobus Maree (p. 41) • Notes from TIMSS-R (p. 41) • Girls and boys on a par, Éva Plagányi-Lloyd and Jennifer Case (p. 41) • Reading, maths, and gender equality (p. 42) 43
Regulars Fact files More on the Arctic narwhal (p. 25) • Bird nectars in flowers (p. 31) • TB facts and stats (p. 33)
Maths and environmental science Johan C. Pauw
Out of the classroom, into the field, Dumile Tshingana (p. 43) • The why (and how) of biomaths, Henri Laurie (p. 45) Viewpoint How bad is ‘child labour’? Michael Bourdillon
Science news Spider webs for hungry times; Brain food (p. 12) • Energy options; How smoke affects cloud cover and climate; Fact and fiction (p. 24) • The case for early antiretroviral therapy for HIV/AIDS – Brian Williams and John Hargrove (p. 36) 13
Your QUESTions answered Life on planet Earth? – Maarten de Wit and Phil Charles • Reducing greenhouse gases – Harold Annegarn • Boiling water – Phil Charles
Letter to QUEST Innovate and educate
The S&T tourist Not just elephants at Addo Megan Bradfield
Books Proxima: The Nearest Star (other than the Sun!) • Aloes in Southern Africa • and other titles
Diary of events
ASSAf news QUEST: the first four years; Wind power; People on the move; On teaching evolution
Back page science • Mathematical puzzle
What’s really best for the children?
Watching whale-tusks grow Martin Nweeia and Francis Thackeray Measuring the amazing tusk of the Arctic narwhal
Drug-resistant TB in South Africa Bavesh Kana and Digby Warner
Getting back to basics
The drinking habits of sunbirds
Diamond and mammography screening Tom Nam Improved measurement of X-ray doses
Quest 4(3) 2008 1
SCIENCE SCIENCE FOR FOR SOUTH SOUTH AFRICA AFRICA
ISSN 1729-830X ISSN 1729-830X
VOLUME 4 • NUMBER 3 • 2008 VOLUME 3 • NUMBER 2 • 2007 R29.95 R20
Wonder werk C ave and Africa’s pa st
I nve st ing in se e d s Foo d f or hea lt h Get t ing a hea d wit h mat h s C hild la b our
A C AACDAEDMEYM YO FO FS C I EI ENNCCEE OOFF SS O U TT HH AAFFRRI C I CA A SC OU
View from the base of the main archaeological excavation, looking towards the stalagmite at the entrance to Wonderwerk Cave. Image: Courtesy of Peter Beaumont SCIENCE FOR SOUTH AFRICA
Editor Elisabeth Lickindorf Editorial Board Wieland Gevers (University of Cape Town) (Chair) Graham Baker (South African Journal of Science) Phil Charles (SAAO) Anusuya Chinsamy-Turan (University of Cape Town) George Ellis (University of Cape Town) Jonathan Jansen (Stanford University) Correspondence and The Editor enquiries PO Box 663, Noordhoek 7979 Tel.: (021) 789 2331 Fax: (021) 789 2233 e-mail: email@example.com (For more information visit www.questsciencemagazine.co.za) Advertising enquiries Barbara Spence Avenue Advertising PO Box 71308 Bryanston 2021 Tel.: (011) 463 7940 Fax: (011) 463 7939 Cell: 082 881 3454 e-mail: firstname.lastname@example.org Subscription enquiries Meg Kemp and back issues Tel./Fax: (021) 804 7637 e-mail: email@example.com Copyright © 2008 Academy of Science of South Africa
Onward, ever onward A
s technology advances and knowledge accumulates, science keeps moving forward and people get to understand the world better than before. This issue of QUEST ranges over many fields, as researchers explore the distant past; find ways to make the most of the present; and attempt to build a better and healthier future. The Department of Science and Technology’s designation of September as “African Origins” month launches our cover story, which explains southern Africa’s remarkable and little-known association with the earliest beginnings of technological and cultural advances of Homo sapiens (p. 3). August was designated “Marine Biosciences” month, celebrated here by the way in which scientists work together to measure and examine the remarkable tusk of the narwhal whale (p. 25). In addition, it’s the month that brings women to the fore each year. The special careers emphasis on the importance of mathematics in preparing for different types of work (p. 38) features the latest research that gives the lie to any notion that women are any less talented or able in this sphere than men (p. 41). We also highlight the use of diamond to improve the way in which X-ray doses are measured in mammography screening (p. 27). The special suite of articles on nutrition (p. 14) explores holistically the interactions between diet and lifestyle as they affect the health of South Africans. Researchers find ways to make sure that there’s enough iron in the staple foods that people eat (p. 16); explore the relationships between nutrition and exercise (p. 18); uncover the intricacies of blood-clot formation (p. 20); and identify ways in which nutrition can help children with HIV/AIDS (p. 22). Good health also depends on overcoming our worst killer diseases – with updates on the battle against drug-resistant tuberculosis (p. 32), and the arguments for early antiretroviral therapy in treating people infected with HIV (p. 24). Remarkable nature surprises once again with the amazing physiology of sunbirds as they imbibe vast quantities of nectar and liquid to sustain themselves (p. 28). Biotechnology triumphs as the complex tool that South African scientists have been using to preserve the life contained in seeds that’s been considered until recently to be incapable of being stored (p. 8). And by way of turning preconceptions on their heads, a study of the effects of child labour comes up with some surprising evidence as to what’s really best for children (p. 48). With this celebration of science in its astonishing variety comes my farewell as outgoing editor of QUEST, leaving now, after the magazine’s first four years (p. 54) – with grateful thanks to all who have supported our activities and smoothed the path in so many countless ways.
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2 Quest 4(3) 2008
Join QUEST’s knowledge-sharing activities Write letters for our regular Letters column – e-mail or fax your letter to The Editor. (Write QUEST LETTER in the subject line.) ■ Ask science and technology (S&T) questions for specialist members of the Academy of Science to answer in our regular Questions and Answers column – e-mail or fax your questions to The Editor. (Write QUEST QUESTION in the subject line.) ■ Inform readers in our regular Diary of Events column about science and technology events that you may be organizing. (Write QUEST DIARY clearly on your e-mail or fax and provide full and accurate details.) ■ Contribute if you are a specialist with research to report. Ask the Editor for a copy of QUEST’s Call for Contributions (or find it at www.questsciencemagazine.co.za), and make arrangements to tell us your story. To contact the Editor, send an e-mail to: email@example.com or fax your communication to (021) 789 2233. Please give your full name and contact details. ■
Discovering the deep African past at Wonderwerk Cave Peter Beaumont and John Vogel examine the archaeological remains of Wonderwerk Cave in the Northern Cape. They come up with dates suggesting that it’s in southern Africa that the technological and cultural advances associated with Homo sapiens began.
or a long time, it was believed that, during at least the last 50 000 years, sub-Saharan Africa had been a biocultural cul-de-sac, into which new peoples and ideas from elsewhere filtered down, eventually to stagnate at its southern end. Evidence from Wonderwerk Cave in the Northern Cape, however, tells a very different story – it suggests that it was in fact in this part of the world that the new ideas were born and then migrated northwards. Perceptions about the biological cul-de-sac began changing in 1972, when our revised radiocarbon timescale1 showed that southern African Stone Age cultures were, if anything, more advanced than those of the same age in other parts of the world. What triggered our thinking in particular was our finding that the ritual burial of a modern human infant from Border Cave in KwaZulu-Natal dated back to before 48 000 years ago – which, at the time, told us that these remains were older than any skeletal trace of Homo sapiens outside Africa. In 1978, we advocated a sub-Saharan genesis of modern humans, who later dispersed out of Africa around 65 000 years ago, subsequently occupying Europe and contributing to the demise of the Neanderthals there2. Further progress in solving the problem of where and when H. sapiens actually originated, however, needed a far longer timescale than radiocarbon dating could produce. Constructing it became feasible when we applied newer dating methods at two key sites in South Africa. The first was Border Cave, where excavations by one of us (PB) and volunteers in 1970–1971 1. J.C. Vogel and P. Beaumont, “Revised radiocarbon chronology for the Stone Age in South Africa”, Nature, vol. 237 (1972), pp. 50–51. 2. See P.B. Beaumont, H. de Villiers, and J.C. Vogel, “Modern man in sub-Saharan Africa prior to 49 000 years B.P.”, South African Journal of Science, vol. 74 (1978), pp. 409–419. For more on the diaspora, read A.G. Morris, “Human origins and the African connection”, in Quest vol. 3(2), pp. 18–19.
Top: A view upwards from the base of the main excavation at Wonderwerk Cave, showing the depth of the deposit, mainly in the form of fine dust, that accumulated since early inhabitants first moved in a million years ago. Above: In the front of Border Cave, high up on the steep western side of the Lebombo mountain range between KwaZulu-Natal and Swaziland. All pictures courtesy of Peter Beaumont
Some working definitions The term modern human as used here refers to a member of the species Homo sapiens* (which includes all people living today). The term human also includes the now extinct species belonging to the genus Homo. It does not, however, include the earlier genus Australopithecus, of which many skeletal parts were found at Sterkfontein and elsewhere, near Krugersdorp, in the Cradle of Humankind World Heritage Site. (Together, these two genera are classed as ‘hominids’.) Stone Ages are terms used for periods in the prehistory of a region as defined by the presence of certain characteristic stone tool forms by humans. Early Stone Age (as used here) is characterized by handaxes. Middle Stone Age defines a period of more sophisticated tools – for instance, flakes struck off a larger stone core in the form of points. * The name Homo sapiens comes from Latin homo (meaning ‘man’) and sapiens (meaning ‘wise’.)
Quest 4(3) 2008 3
Above: Excavation in progress of the lowest levels of the Border Cave sequence, the lowest unit of which has an age of over 180 000 years ago.
the site were underlain by a then poorly-known culture called the Fauresmith. The Fauresmith had been ascribed by various researchers as belonging either to the Middle Stone Age or to a previous period. Our task was to attempt to give more reliable dates to this Middle Stone Age and the Earlier Stone Age that came before it.
Above right: View from near the large entrance stalagmite at Wonderwerk Cave, showing the extent of the main excavation; the only area in which lower as well as upper stratigraphic Major Units were present. Right: Map showing the location of Wonderwerk and Border caves. ▲
had revealed what appeared to be a complete sequence of Middle Stone Age artifacts. Then came further fieldwork in 1987, retrieval of relevant archaeological samples, and a visit by experts from abroad (arranged by JV), which led to many dozens of dates. These now provide a Border Cave chronology extending back to about 240 000 years ago. At the second site, Wonderwerk Cave, the objective was to press even further back in time, as we knew that the Middle Stone Age levels at
The stratigraphic sequence at Wonderwork The 6-m-deep Wonderwerk Cave deposit has 9 levels or groupings of strata – Major Units (MUs) – which we numbered from the surface downwards, that is, from the youngest level, MU1, to the deepest and oldest one, MU9. Each MU’s special characteristics depicted part of the story of what was going on at that time in prehistory. MU 1: Artifacts from this unit indicated a series of San-linked stone cultures, which radiocarbon dating results placed at 900–2 000 and 2 000–11 500 years ago, respectively, followed by sporadic Khoi herder visits. MU2: This level – the second level down – contained traditional Middle Stone Age material, defined by the absence of handaxes and the presence of pointed tools (that is, ‘convergent points’). Uranium-series readings dated these artifacts at dates ranging between 70 000 and more than 220 000 years ago. MU3: The upper reaches of this unit produced late Fauresmith artifacts, including convergent points and crude handaxes, with uranium-series dates of 276 000–286 000 years ago. MU4: This level contained classic Fauresmith specimens, comprising still earlier convergent points, and small handaxes, which uranium-series and other evidence placed at circa 500 000 years ago. MU5-8: The number of artifacts from these levels was too small for purposes of classification, but those from MU7, with a palaeomagnetic age of 780 000 years ago, are best ascribed to a time late in the Earlier Stone Age. MU9: Palaeomagnetic results show that the upper reaches of this unit date to at least 990 000 years ago, below which, ranging down to bedrock, are a few stone flakes, indicating human occupation, even at that early time.
4 Quest 4(3) 2008
Exploring Wonderwerk Wonderwerk, our focus in this story, is a vast 2 400-m2 tunnel-like cave that runs horizontally for 141 m into the base of a low koppie on the eastern flank of the Kuruman Hills, some 45 km south of Kuruman. This cave was first recorded by the traveller, Henry Methuen, who, when he visited it on 15 July 1844, recorded that “a massive stalagmite ... arrested our eye on first entering” and that many still-extant “drawings ... representing game animals ... garnished the walls”. Pierre Bosman, the original farm owner, lived in the mouth of the cave with his family from 1909–1911 while building the present nearby farmhouse, and later used it as a cart-house and a winter shelter for his sheep until the 1930s. A Second World War fertilizer shortage led his brother (and associates) to exploit the cave commercially for supposed ‘bat guano’ between 1940 and 1944. During that time, much of the floor backwards of 31 m in the cave was dug over to the depth of up to 2.5 m, with digger finds leading to short archaeological studies over the next three decades3. In December 1978, Beaumont began his timescale-linked research at Wonderwerk Cave to establish the cultural sequence of events. An excavation spanning the youngest levels was conducted by Francis and Anne Thackeray from July–October 1979. Then, from 1980–1996, during fieldwork trips, the excavation was taken down to bedrock, about 500 m3 of disturbed digger debris was removed from deeper in the cave, and six further trenches were sunk into the underlying intact sediments there. After that, from 1997 to the end of 2002, came the task of washing, marking, and studying the retrieved material. The protracted, painstaking effort (with the 3. The digger finds sent to the now defunct Bureau of Archaeology were studied by B.D. Malan in May 1940, by Malan and Wells in January 1943 and November 1944, by Malan and University of California African Expedition members in May 1945, and by Carl Butzer at times from 1974–1977.
Dating in archaeology
Above: The task of sorting the retrieved material at the McGregor Museum took five years to complete, owing, in the main, to the many small mammal bones from some levels and areas.
* The radioactivity of these elements decay at a constant rate given by the half-life of the isotope involved. ** An isotope is the name given to each of the forms of an element that differ from one another in relative atomic mass, and in nuclear (but not chemical) properties – that is, they have the same number of protons and electrons, but differ in the number of neutrons. *** Water dripping down to form stalagmites contains calcium carbonate and traces of other substances, including uranium.
help of 6–9 assistants who came each time from Kuruman) revealed that the Wonderwerk deposit was 6 m deep, made up of 9 stratum groupings or Major Units (MUs), which we numbered from the surface downwards (from the youngest level, MU1, to the deepest and oldest one, MU9). We set about dating the strata, as well as their contents, using all the various dating methods – and applying as many of them as we could in each case, to check for consistency and make certain our dates were reliable. Taken together with other evidence, our findings suggest that, in central South Africa, the Middle Stone Age ranges from 45 000 to circa 250 000 years ago, the Fauresmith from c. 250 000 to c. 500 000 years ago, and the Earlier Stone Age preceding that. The firm dates that our measurements yielded show the extraordinary uniqueness of Wonderwerk Cave – it was occupied by our ancestors for an amazing million and more years, far longer than any known cave on Earth. And the cultural content showed that Stone Age technology in this part of the world was more sophisticated than anywhere else on Earth at the time. Southern Africa, we now believe, was not only the cradle of human evolution, but of modern human technological and cultural development as well.
Dating archaeological material involves establishing the age of the object or material itself, or dating it by dating the surroundings in which it was found (assuming that it had remained there without being disturbed), or matching the object with similar objects found elsewhere whose date is known. For the most part, the absolute dating of archaeological sites is based on the decay of radioactive elements occurring in nature*. The most accurate technique is Above: John Vogel preparing a radiocarbon sample in that of radiocarbon dating, the QUADRU laboratory at the CSIR, a facility that was which makes use of the minute, crucial to research on the African past. but relatively constant amount of radioactive carbon atoms in all living plants and animals. These C-14 isotopes gradually decay with a half-life of 5 730 years so that, by measuring their concentration in fossil material such as charcoal or bone, the age of that fossil material and the level in which it was found can be deduced. This method gives ages up to about 50 000 years ago; there is hardly any detectable radioactivity from carbon in anything much earlier than this. For older stratigraphic levels, uranium-series dating can be used. Uranium decays extremely slowly through a series of intermediary elements, ultimately to a stable lead isotope**. By analysing the uranium and lead isotopes in igneous rocks, a timescale for (especially) the older geological formations has been established. Uranium also provides a means for shorter-term dating. When calcium carbonate is precipitated – for instance, as a stalagmite – traces of uranium are incorporated*** and the first decay product of the isotope U-234 (namely Th-230) gradually accumulates until it reaches a steady state after 300 000 years. By measuring the uranium and thorium isotopes, the age of the sample can be determined. At Wonderwerk Cave, the initial stage of stalagmite formation developed at several levels in the deposit, and they provided a date of circa 250 000 years for the transition from the Fauresmith deposits (representing an intermediate stage of development between Earlier and Middle Stone Age) to the actual Middle Stone Age. Two further techniques, luminescence dating and electron spin resonance dating (ESR), make use of the fact that radioactive radiation from surrounding deposits tend to dislocate electrons in the crystal structure of minerals. The ‘excited’ state of the buried sand grains caused in this way can be emulated by exposing them to heat or light. During the process, light flashes are emitted, and, by recording this thermo-luminescence (TL) when heat is applied, or optically stimulated luminescence (OSL) when the grains are exposed to light, we can deduce the total radiation dose since the time of burial, and calculate the age of the deposit. (The longer the grains have been buried, the greater the number of electrons that are displaced from their equilibrium state or condition, and the more light flashes are emitted when heat or light are applied.) Currently, ESR dating is being applied to tooth enamel from excavated animal teeth. The extent of the electron displacements is directly recorded and, together with the knowledge of the dose rate of the radiation, the time of burial is obtained. The dating range of both of these methods depends on the radioactivity at the site, which can be variable, but dates as far back as 200 000 years ago are being reached. Potassium-argon dating, used for volcanic material, has provided dates for the earlier periods of hominid evolution. It is based on the radioactivity of the potassium isotope K-40, which decays slowly to Ar-40. By measuring the minute amounts of this noble gas in potassium feldspar crystals produced from molten lava, dates in the range of 1–10 million years ago are obtained. South Africa does not have volcanism of this age, but, in East Africa, layers of volcanic ash are present in the sediments containing remains of early hominids, and much effort has been put into dating these levels. The approximate dating of South African sites in this timerange are based on faunal comparisons with East Africa. For example, if remains of an extinct animal species have been identified and dated there, and bones of the same species are found in South Africa, we can assume that the two sets of bones are of similar age. Another method used at Wonderwerk Cave is palaeomagnetic dating. In the past, the north–south direction of the Earth’s magnetic field (aligned along the Earth’s axis of rotation), has repeatedly reversed; this dating technique is based on determining the direction of the Earth’s magnetic field as preserved in the deposit. The last reversal has been dated elsewhere by potassium-argon to 780 000 years ago, and this event is reflected in MU7 of the cave. Further down, in the top of MU9, a brief return to the ‘normal’ field direction (in an event dated back to some 990 000 years ago) has been recorded; it indicates that the Wonderwerk levels below this are even older.
Quest 4(3) 2008 5
Above right: Evidence of fire was present in all Major Units. An ash layer with many burnt animal bones in the top of MU9 represents the earliest known use of fire by humans, about a million years ago. Below: Parallel lines incised on a 2-cm-large stone from a level predating 100 000 years ago. A slab with sub-parallel curved lines also came from MU3 that dated back to 270 000–290 000 years ago. Bottom: The small pebbles, generally less than a centimetre in diameter, that were scattered in a small area of MU4 about 500 000 years ago.
Above: A view from the cave rear after all disturbed digger debris had been removed from there.
Some wonderful findings Archaeological explorations – in general, and at Wonderwerk in particular – take time and patience, as researchers sift through and catalogue the details of what they find, and then submit the material to meticulous analysis. But the rewards come when the meaning of what they have found is revealed. At Wonderwerk, many treasures were uncovered during the decades of work, and much new knowledge has come to light. Cave extensions
As we worked at the very back of the cave, where almost no natural light penetrates, we exposed the mouth of a 2-m-wide tunnel, previously hidden by a build-up of deposits. Leading off to the left was a large chamber that, over time, had filled with deposit almost to its roof. At the entrance, we found charcoal fragments and Fauresmith artifacts, indicating that early humans with burning brands had – for reasons as yet unknown – often entered what could be a series of caverns further in, more than 270 000 years ago. Cave aridity and preservation of organic remains
We measured the amount of water dripping from the roof at the rear of the cave. We found that it amounted to a mere 0.4 litres per week, which translates into a mean water influx, over that 2 000 m2 area, of far less than a millimetre per year. This extreme aridity caused superb preservation of organic items, as shown, for instance, by 800 000-year-old horn fragments of an extinct antelope that still retain their keratin sheaths4, and an area of humified5 grass bedding on which humans slept some 400 000 years ago. Engraved stones and the birth of art
In MU1, we found 20 engraved stone slabs, often deliberately broken afterwards, that all show patterned lines (except for one with a zebra rump marked by a ‘wound’), and in MUs 2–4, we recovered other such slabs, mainly with spaced parallel lines, indicating an engraving tradition extending to as far back as 500 000 years ago. From these
latter findings, we inferred that such markings may also have survived on resistant rocks out in the open, to reveal a diversity of patterns that characterize this formative phase in the birth of art. Exotic stones
In MUs 2–4, in the front of the cave, we found single clusters of small rounded quartz and chalcedony pebbles, the nearest known source of which is the Kuruman River over 45 km away; the same units at the back of the cave yielded mainly quartz crystals, known to occur more than 20 km to the northeast. Such gathering was sustained over a long period of time, despite the effort involved in retrieving those items across such distances. It suggests behaviours similar to those in later times – such as placing offerings at a shrine, or throwing coins into a fountain – and that beliefs not dissimilar to our own were perhaps held by Wonderwerk’s occupants. Ancient fire
Last, but not least, were the pervasive signs of the use of fire, which we discovered throughout the sequence. The earliest firm occurrence was from upper MU9. Here, an extensive ash sheet containing hundreds of burnt bone fragments of a zebra-sized animal clearly attests to a million-year-old braai! This, and an occurrence of similar age at Swartkrans (near Krugersdorp), represent the earliest clear evidence that we have at present for the taming of fire by humankind6. Environmental change Those many years of digging at Wonderwerk have led to some key deductions – one of them on regional environmental change. During the coldest interval of the last Ice Age, from 70 000–12 000 years ago, mean subcontinental temperatures dropped to some 6 °C lower than they are now, and rainfall in the central interior fell to about 40% of what it is at present. These conditions caused Kalahari sands to move, regional water sources to dry up, and Wonderwerk to be abandoned by its human inhabitants. On the other hand, evidence provided by pollen records, high-level river silts, and the
4. Keratin sheaths form the outer covering of the bone in the antelope horns. Keratin is a fibrous, sulphur-containing protein that occurs in the outer layer of the skin as well as, for instance, in hair, nails, feathers, and hooves. 5. Humified material (or humus) is a mass of partially decomposed organic matter. 6. These indications of the taming of fire were followed, elsewhere, by comparable findings at an 800 000-year-old site on the banks of the Jordan in Israel, and localities in western Europe with ages ranging back to 400 000 years ago.
6 Quest 4(3) 2008
A note for visitors Wonderwerk Cave was declared a National Heritage site in August 1993. There is a resident guide, and facilities include an ablution block, a small museum, and chalets for hire. For bookings, phone Susan Joubert at 082 832 7226 or (053) 712 1691.
Left: This lower jaw fragment of a modern human has been directly dated to 74 000 years ago. (Excavated from Border Cave.)
species composition of small mammal bones, show that, some 6 000 years ago, when temperatures were about 1 °C above those of today, the abundance and diversity of trees increased, the lower Vaal was prone to massive floods, and regional rainfall rose by at least 25%. If, therefore, rainfall responds to temperature increases in the same way in the future as it did in the past, we may anticipate that the current rise in temperatures due to human activities will again result, over the next few decades, in high precipitation over the summer rainfall region of southern Africa. Modern human origins Wonderwerk findings also bring further understanding of the timing and location of modern human origins. Two sets of reliable uranium-series dates from the cave provide firm evidence bearing on the problem of where the epicentre of cultural innovation was in the ‘old world’ during the period immediately prior to the first appearance of modern humans. One set of dates indicates that handaxes were last made in South Africa about 270 000 years ago, but went on being made in East Africa and Europe up to 130 000 and 40 000 years ago, respectively. This would indicate a northward lag of up to 220 millennia in the demise of this ancient tool-type. In other words, the area that is now South Africa seems to have been the first, by far, to leave handaxes behind and to move on to more sophisticated tools. The other set of dates shows that ‘convergent points’ were present here by 500 000 years ago, whereas they first appear in East Africa and Europe much later – after about 240 000 years ago. In this case, the Wonderwerk findings indicate that it took over 260 millennia for areas further north to introduce this new tool form. Our dating and our age estimates clearly indicate that – in the period leading to the advent of H. sapiens – the subcontinent was a focal area of cultural innovation, from which new ideas drifted slowly northwards, and not a dead end, as previously thought. Studies (especially of DNA) since the late 1980s provide compelling evidence that modern humans arose in sub-Saharan Africa at the onset
of the Middle Stone Age, which we now believe (from our ‘molecular clock’ estimate based on the Wonderwerk evidence) to have begun prior to 200 000 years ago. Two interlinked messages now unite from our past – the first provided by our datings, the other by DNA genetic studies – that are here taken to indicate that humans, modern in body and behaviour, were the culmination of a long biocultural forging with origins in the game-rich temperate savannas of southern Africa7. The evidence further indicates that, from this ultimate homeland, a diaspora took place about 240 000 years ago, leading, over the next hundred millennia or so, to the complete occupation of sub-Saharan Africa by H. sapiens. After that, some 68 000 years ago, a small, more northerly group of these people were driven by a period of severe aridity to a second dispersal; they left Africa by a Red Sea crossing, and the result was the colonization of Australia by 60 000 years ago, followed by East Asia, and then Europe after 45 000 years ago. Later came the entry into the Americas, at or before 13 000 years ago, and the discovery of various remote islands over the past few millennia. This completed the H. sapiens occupation of all the Earth, 10 000 or so generations after the original party left humankind’s hitherto unrecognized southern Eden in Africa. ■ Peter B. Beaumont is a research associate at the McGregor Museum in Kimberley. He has spent many years studying the prehistory and palaeoclimates of the Northern Cape. Dr Vogel was invited to run a radiocarbon dating laboratory at Groningen in the Netherlands. He subsequently returned to set up and direct the world-renowned Quaternary Dating Research Unit (QUADRU) at the CSIR in Pretoria, where he produced many of the dates discussed here. Support for this research was provided by the Anglo American and De Beers Chairman’s Fund, the Human Sciences Research Council, and the Kalahari District Council. Thanks are also due to the Nieuwoudt family for their hospitality, and for their donation to the nation of Wondewerk and the land immediately surrounding it.
For more about Wonderwerk Cave, read P.B. Beaumont and J.C. Vogel, “On a timescale for the past million years of human history in central South Africa”, South African Journal of Science, vol. 102 (2006), pp.217–228. For wider background, consult S. Oppenheimer, Out of Africa’s Eden: The Peopling of the World (Jonathan Ball, Johannesburg, 2003).
Top: Use-wear damage suggests that convergent points were used to tip stabbing spears, and were made in central South Africa from 500 000 to 30 000 years ago. The one illustrated here is 8 cm long. Above: Handaxes were all-purpose tools, mainly used for butchering, that were made, subcontinentally, between c. 1.6 and 0.26 million years ago. The one illustrated here is 23 cm long.
7. For further details, read Alan G. Morris, “A KhoeSan survival story”, in Quest vol. 3, no. 3 (pp. 16–19).
Quest 4(3) 2008 7
Storing and restoring
Above: Ripening (red) and ripe (black) fruits of Acokanthera oblongifolia, a recalcitrant-seeded species. Photograph: Patricia Berjak Right: Seeds of the cycad Encephalartos natalensis on the cone scales. Photograph: Denise Berjak
The world is losing its plant biodiversity at an alarming rate. Scientists on every continent are working on ways to store and conserve the genetic resources of plants. Pat Berjak explains what’s involved in low-temperature preservation of hithertounstorable seed material from some of Africa’s valuable species.
Below: Strelitzia regina, which produces non-orthodox seeds small enough to be cryopreserved intact. Photograph: Patricia Berjak
frica’s extensive flora includes many species that grow nowhere else in the world1. Tropical and sub-tropical forests, for instance, are rich natural repositories of species diversity with great economic and cultural value. Many individual species are esteemed in symbolic cultural contexts. Many have great value in traditional medicine, which is used by about 80% of South Africans – trade in muthi plants in Durban alone is worth R280–350 million a year2. It is crucial for such plants to be preserved. With growing urbanization, demand for muthi plants in South Africa’s cities has soared. The rush to supply the market has obscured indigenous wisdom about sustainable harvesting, so extensive bark-stripping and bulb collection have placed many wild species on the endangered list. The status of the pepper-bark tree (Warburgia salutaris) salutaris is a case in point. The bark is the soughtafter commodity, but it has been gathered at such high levels
that the species has now disappeared, except in protected areas. To make matters worse, KwaZulu-Natal’s pepper-bark fruit, as it develops, is parasitized by insect larvae, resulting in loss of mature seeds. This extreme example of W. salutaris illustrates the pressure on many African tree species, and emphasizes the need to conserve them. Genetic diversity of tree species on the African continent is both high and invaluable. Yet the rate of diversity loss is also high, through deforestation, the fragmentation of ecosystems, over-exploitation – and potentially through global warming. How can we best look after plant biodiversity, not just for the sake of preservation, but in terms of sustainable use? The answer lies in seed storage, which is the most effective and widelypractised means of ex situ (outside the natural environment) conservation of 1. With its range of climatic zones, the continent’s floristic diversity is unevenly distributed. The Ténéré in the Sahara, covering 200 000 km2, has only 20 vascular plant species (that is, plants having an internal conducting system for water and nutrients), whereas South Africa’s Cape Floristic Region, for example, is home to more than 9 000 species in an area of 90 000 km2. Together, the remarkably rich flora of southern and tropical Africa exhibits among the highest species densities in the world. For more on South Africa’s remarkable species diversity, read “Discovering our biodiversity” in Quest vol. 2 no. 4 (2006), pp. 3–10. 2. For more on the trade in traditional medicinal plants, see “Cultivating health and wealth” by Tony Dold and Michelle Cocks in Quest vol. 1 no. 2 (2004), pp. 16–17.
plant-life from seeds Orthodox seed storage at –18 °C, and the Svalbard Global Seed Vault The rule for orthodox seed storage is, ‘the colder the better’. While cryostorage affords the lowest temperatures (at –196 °C), most seed banks use freezers (walk-in freezers are best) set at –18 °C, a temperature at which dry orthodox seeds may be safely stored for years to decades. Seed collections (accessions) are commonly split, with part of the sample stored in a regional seed or gene bank, and a back-up sample in a central repository which, for the SADC countries, is in Lusaka in Zambia. Splitting accessions in this way means that, in case one collection is ever destroyed, another is available from which plants can be grown and seed accessions replenished. Global concern about both anthropogenic and natural disasters has given rise to a new ‘insurance’ development, which became operational earlier this year – the Svalbard Global Seed Vault. Built deep into a mountainside on the Norwegian island of Spitzbergen in the Svalbard Archipelago (78° 0” N, 17° 0” E) in the Arctic Ocean, the vault uses the frozen landscape that maintains the seed storage chambers at –5 °C, without the aid of artificial cooling. As it is widely recognized that still colder temperatures will extend seed storagelifespans further, cooling units bring the vault’s temperature – as well as some 10 m of the surrounding rock – down to a low of –18 °C. Although built to withstand all foreseeable catastrophes (hence its popular name, the Doomsday Vault), the Svalbard Seed Vault operates on the same principles as regional and national seed storage facilities for conservation at –18 °C, and regeneration of plant genetic resources. It is, however, truly global, offering a ‘safe haven’ for replicate samples of seeds already stored in national and regional facilities the world over, with samples from South Africa already banked there. This vault is also different in that, even if the cooling units fail, its permafrost environment ensures that the temperature would remain well below 0 °C. The Svalbard Global Seed Vault is built 150 metres above sea level, where (it has been calculated) no flooding would occur, even if the Greenland ice sheet were to melt. This seed vault is a prime example of “making assurances doubly sure” (as averred by William Shakespeare) – or, where duplicate samples are already held, assured in triplicate!
plant genetic resources. But some seed material is particularly hard to store, so new biotechnological processes are being developed and refined, in response to the challenge.
Ultra-cold preservation Storing seeds at low temperatures – cryostorage – is used for what are known technically as ‘orthodox’ and ‘recalcitrant’ seeds. Orthodox seeds are dry seeds, characterized by their desiccation tolerance, and, as long as they are of good quality, can be stored for long periods at low temperatures (ideally –20 °C or lower) and low relative humidity (RH). Under optimal conditions, provided by seed-banking cryostorage in liquid nitrogen at –196 °C, these periods can be decades or even centuries. Although cryostored seeds are not immortal, this method has the best potential for long-term conservation of plant genetic resources. Recalcitrant seeds is the collective name for desiccation-sensitive seeds. They belong to a relatively wide spectrum of unrelated plant species producing seeds that not only do not dry out, but cannot do so without lethal
3. The Convention on Biological Diversity (CBD) – or, the Rio Treaty – is an international treaty adopted in 1992 at the Earth Summit in Rio de Janeiro. Its three main goals are the conservation of biological diversity (or biodiversity); sustainable use of its components; and fair and equitable sharing of benefits arising from genetic resources. Often regarded as the key document relating to sustainable development, this treaty, for the first time in international law, recognized the conservation of biological diversity as “a common concern of humankind” and integral to development. It covers all ecosystems, species, and genetic resources, linking traditional conservation efforts to the economic goal of using biological resources sustainably.
Top: Highly recalcitrant seeds of the Natal mahogany (Trichilia dregeana). Photograph: Norman Pammenter
The seed storage cure Seed storage is imperative for genetic resource and plant biodiversity conservation, as well as for ensuring future stocks of food, feed, and planting material. It is taken very seriously – Target viii of the Convention on Biodiversity’s Global Strategy for Plant Conservation3 aims at having 60% of threatened plant species in ex situ conservation by 2010. Random seed collection and storage under uncontrolled ambient conditions are not good enough. Effective seed storage – otherwise known as germplasm (genetic resources) conservation – comes from knowledge, gained from rigorous experimentation, about the biology and consequent responses of seeds. It involves a series of complex processes, based on understanding just how different kinds of seeds behave in different conditions. Until a decade ago, little was known about the reproductive biology and seed
responses of most of the thousands of African species – although the situation is gradually improving. The more we discover, the better we can design and refine the processes that make for greatest success.
Middle: Although not a threatened species, this amaryllid (Clivia miniata var. citrina) is harvested for the roots, from which preparations are made to treat snakebite, and as a drink to treat febrile conditions and ease childbirth. Photograph: Patricia Berjak Above: Cyril Makhathini studies the Red Data lists of endangered plant species. Photograph: Denise Berjak
Quest 4(3) 2008 9
Left (from top down): A tiny excised axis of Mimusops caffra. In vitro explants of cocoa (Theobroma cacao).
Photograph: Denise Berjak
Photograph: Denise Berjak
Cape ash (Ekebergia capensis) explants in rooting medium in vitro.
consequences. These cannot be stored in the same way as orthodox types. Cryostorage is a major focus of our research programme at the University of KwaZulu-Natal in Durban, particularly for the germplasm of species that produce recalcitrant seeds. We have found that these are always metabolically active, and that their metabolism grades smoothly from development into germination4, which is one of the main reasons for their sensitivity to drying. Germination is initiated without the need to add further water, which imposes tremendous problems for even shortto medium-term storage, as seedlings in the process of development are not a storable resource. Another problem is that virtually all tropical and sub-tropical seeds (whether orthodox or recalcitrant) harbour fungi. Fungi become temporarily inactive in cryostored, dry, orthodox seeds, but they proliferate on, and in, hydrated recalcitrant seeds – especially under the high RH conditions that are essential to prevent the seeds from losing water. But recalcitrant seeds of many species are sensitive to low temperatures, so, for them, coldstorage is not an option, as they are lethally damaged by chilling. Temperatures at which such seeds are stored are generally not lower than 15 °C: in these conditions, both seed and fungal metabolism remains active. Many of the African plants that are highly prized for traditional medicine and cultural purposes produce recalcitrant seeds. For example, members of the Amaryllidaceae produce bulbs, many of which are harvested for medicine, and many of these species produce recalcitrant seeds. Over-harvesting of these geophytes5 in the veld – coupled with the fact that their seeds are shortlived – could seriously threaten their continued survival. Tree and shrub species are also in jeopardy, such as W. salutaris, which is under such pressure that no natural populations of trees exist any longer except in nature reserves. Halting the fade to oblivion So how can we help to ensure that such valuable species do not fade
Photograph: Patricia Berjak
into oblivion? How do we go about conserving the genetic resources – generally best offered in ‘natural packages’ called seeds – even though they may be recalcitrant? Answers are emerging from our research on recalcitrant seeds, which includes developing protocols for the cryopreservation of the genetic resources of individual species6. Using biotechnological approaches to ameliorate this pressing environmental problem is full of complexities. The process involves transferring an appropriate section of living tissue (referred to as the explant) from its natural site (the living seed) to a culture medium (a nutrient material in which the tissue can be preserved). The first thing to take into consideration is that, for partiallyhydrated living tissue to survive immersion in liquid nitrogen, its volume must generally be not much bigger than a cubic millimetre. But recalcitrant seeds are on the whole large – mostly far larger than familiar orthodox seeds. Such as the seeds of mangos, avocado pears, and the coconut, all of which are recalcitrant! So, obviously, whole seeds can rarely survive immersion in liquid nitrogen, although occasionally this is possible, as, for example, seeds of W. salutaris. In most cases, only a small segment of a large recalcitrant seed can be used as the explant designated for cryopreservation. The explant of choice is the embryonic axis, that is, the root–shoot continuum that is capable of giving rise to a new plant. This means that the axis, which is normally very small, must be cut away (excised) from the cotyledon(s) – that is, part of the embryo in a seed plant that generally, but not always, contains all the stored food reserves required by the growing axis for the establishment of a seedling. Before doing anything else, therefore, we need to develop an in vitro (tissue culture) medium that will supply the excised axes with all the nutrients and other requirements for germination and seedling establishment. This medium generally needs to be designed to suit the specific needs of individual species. For technical
4. In orthodox seeds, developmental metabolism ‘switches off’, the seeds dry out naturally, and metabolism associated with germination starts only when water is again taken up. In recalcitrant seeds, no switch-off occurs, so germinative metabolism succeeds that of development, without any break. 5. A geophyte is a perennial plant that propagates by means of buds below the soil surface. 6. The ultimate objective is to establish a Cryoconservation Centre, catering for safe preservation and dissemination of the genetic resources of the many species producing non-orthodox seeds. Such a centre would serve not just South Africa, but extend to the whole sub-Saharan African region. This objective is supported by the UK government’s Darwin Initiative in collaboration with the Millennium Seed Bank at Kew, outside London.
10 Quest 4(3) 2008
Right: Lubaina Essack setting up drip irrigation for cocoa saplings, in the sterile, temperature-controlled greenhouse. Photograph: Patricia Berjak Right below: Fungal infection in a culture, as a result of which all these germinated axes have to be discarded. Photograph: Vishal Bharuth
reasons for some species, we have to use explants as an alternative to the embryonic axes7. Overcoming contamination The persistent presence of fungi in the short-term storage of intact seeds at high RH dooms in vitro axis culture to failure. Before axis excision, therefore, the seeds must be surfacedecontaminated, through the use of one (or more) of a range of sterilants. As the contaminants occur not only on the exterior but also within the seed, the axis surface must similarly be decontaminated after it has been excised. There is a danger that one or other commonly-used sterilant could damage the delicate axis tissue, however, so the effects must be carefully evaluated, and the type and concentration of the sterilant, as well as the duration of treatment have to be designed for optimal effect. Fungus may also be located within the axis, leading us to evaluate the use of systemic fungicides (which are taken up into the tissues) as well. But whatever the procedure, anti-fungal treatments must be evaluated both in terms of efficacy and the potential damage they could cause to the axis tissues, which obviously must be minimized. Only when the fungi have been eliminated can one get a ‘clean’ culture of axes – but even then, proliferation of bacteria, previously suppressed by the antibiotic activity of the fungi, might be manifested. Should this happen, the additional use of antibiotics has to be evaluated for their effects on the axes. From the decontamination of the axis to its introduction onto the culture medium, all procedures are carried out in a sterile environment to avoid secondary contamination. Flash dryer to deep cold When the uncontaminated axes show their potential to develop into vigorous seedlings, the next manipulation can begin. This is the partial dehydration of the axes down to a water content level that is suitable for cryopreservation, with no lethal ice crystals forming in the cells. Lethal metabolism-linked injury occurs when recalcitrant material dries slowly, over several hours or days. Our investigations have found, paradoxically,
that desiccation-sensitive axes can withstand sufficient dehydration for cryopreservation – provided that water is removed as rapidly as possible. In 1990, our research team developed a highly effective device we call a ‘flash dryer’, in which air dried by a desiccant is fanned across the excised axes, dehydrating them so rapidly – within minutes or an hour or two at most! – that ice crystals are simply given no time to form. Flash drying has now been adopted by laboratories worldwide. Axes are first sampled at frequent intervals for water concentration, and a drying rate curve is constructed – that is, a curve showing the decline of water content as a function of drying time. At each sampling point, some axes are introduced into tissue culture, to assess their viability after drying at each specific level of water content. It is imperative not to damage the axes by over-dehydrating, and it’s just as essential to achieve a water concentration range that ensures the least possible injury to the explant when it is cooled to the –196 °C temperature of liquid nitrogen. To find ways of minimizing injury further, we are also experimenting with treatments before cooling, using cryoprotectant solutions that increase the viscosity of the axis cell contents, in this way reducing the potential of lethal ice crystals forming as the temperature drops8. Only after establishing the dehydration conditions that govern axis survival after flash-drying can cryopreservation be attempted. At this stage, too, the parameters must be optimized, particularly relating to the rate of cooling – which, to ensure survival, must also ensure sufficiently rapid passage of the explant through the temperature range at which ice crystals form and grow. The point to watch here is the water concentration in the axis: the more water the tissues contain, the more rapid the cooling rate needs to be. But we cannot yet lay down hard and fast rules, as axes of some species inexplicably survive better when the cooling rate is not as rapid as flash-drying can achieve! Whatever the cooling rate, the axes, once frozen, are rapidly transferred under conditions that allow no warming (thawing) to special storage containers (called cryovats) filled with
Retrieval and dispersal The next stage of the process comes when it’s time to bring the axes out of storage again. Care is needed to make sure that axes retrieved from cryostorage survive the thawing and rehydration steps. Thawing, which must be rapid, is normally carried out at 37–40 °C, and we have discovered that a particular solution containing calcium and magnesium provides the best medium for thawing. We also use this solution for axis rehydration, as we have found it best in promoting normal further development of seedlings in vitro. Before we put the newly hydrated axes on a germination medium, we once again surface-sterilize them – in ▲ ▲
7. In most cases, the embryonic axes of recalcitrant seeds are tiny. In a few species, however, axes become very large, and, for preservation, an explant alternative to the axis has to be developed right at the outset. Alternative explants include shoot apical and axillary buds, but a protocol has initially to be developed to ensure that rooted plantlets can be obtained from these sources. Another route is via somatic embryogenesis, a biotechnological procedure ultimately producing genetically-identical embryos from a juvenile tissue of the plant. 8. The more viscous a substance is, the less water it contains to form crystalline ice. Essentially, during cooling for cryopreservation, the objective is to form, within the cells, smooth (vitrified) ice that does not contain crystals.
liquid nitrogen. Theoretically, once the frozen axes have been delivered alive into liquid nitrogen, they should survive for a very long time.
Quest 4(3) 2008 11
Top: Synseeds (synthetic seeds), each containing a single embryonic axis. Photograph: Denise Berjak Above: Post-graduate researcher, Ashika Jaimangal, examining saplings of Cordyla africana in the shade-house. Photograph: Denise Berjak
case they have picked up contaminants during the process. Seedlings that are established in vitro are transferred to sterile soil, then gradually exposed in a greenhouse to ambient RH and other environmental hazards. Only now can the young plants be introduced to the ‘outside world’ and, generally after a phase in the shade-house, planted out in the field9. The next challenge comes when material retrieved from cryopreservation is destined for faroff locations. Neither transport within cryocontainers, nor the dispatch of material in culture tubes, is logistically feasible. To solve the dissemination problem – which is imperative for our objective of a Cryoconservation Centre for sub-Saharan Africa – we are experimenting with synthetic seed (synseed) production. To manufacture synseeds, we allow the axes a short in vitro recovery period after being retrieved from cryostorage. Each is then sealed in a nutrient-containing gel bead, which, preliminary studies have shown, keeps it vigorously alive for at least a month. Although the axes re-commence development, it is sufficiently slow not to allow the tiny root to protrude from the bead during storage. The synseeds could also be planted directly in sterile soil, to cut out the need for a further in vitro phase at the delivery site.
Plant biodiversity for the future The biotechnological procedures outlined here offer great promise for conserving and re-introducing plant material, and restoring environments. Considering the pressures from both human activity and natural factors, saving plant biodiversity is absolutely essential – and that’s best done through seed banking. High-quality orthodox seeds last decades when stored at –18 °C, but recalcitrant-seeded species need cryostorage. The complex biotechnology involved in explant preservation at such low temperatures is time- and labour-intensive, but there is no other option if we want to conserve the genetic diversity of the many species producing desiccation-sensitive, recalcitrant seeds – and ultimately, the well-being of the Earth itself. ■ Professor Patricia Berjak, based at the University of KwaZulu-Natal, has worked extensively in the field of seed biology, initially on the mechanics of deterioration of stored orthodox seeds, and, for the past 25 years, on recalcitrant seeds. She has strong links with the UK’s Millennium Seed Bank at Kew and the National Center for Genetic Resources Conservation in the USA, and she is president of the International Society for Seed Science. On 25 July 2008, she received the NRF President’s Lifetime Achievement Award “for outstanding scholarship”. For more, consult M. Sacandé et al. (eds), Comparative storage biology of tropical tree seeds (International Plant Genetic Resources, Rome, 2004), and visit www.ukzn.ac.za/plantgermcons
9. We must know that cryostorage has not changed the genetic constitution, and that the plants grown from cryostored axes will be as vigorous as those grown directly from seeds. These experiments are at present ongoing.
News Q Good food guide Spider webs for hungry times Black widow spiders are unique in spinning different kinds of web, depending on how hungry they are, report Jacquelyn Zevenbergen and Todd Blackledge (University of Ohio, USA) – the hungrier the spider, the deadlier the web. Spiders fed daily with crickets spun tangled, nonsticky webs; but spiders the same size, which had been starved for a week, spun sheets connected to the ground by sticky strands, catching insects and suspending them in mid-air, ready for eating. The webs of sated spiders are constructed less to catch prey and more to protect them from predators, the researchers found: “They are adding and deleting architectural features that have specific functions”, Blackledge explains. Source: New Scientist, 28 June 2008.
Brain food Many studies connect intelligence with consumption of omega-3 fatty acids. According to American researchers William Lassek (University
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of Pittsburgh) and Steve Gaulin (University of California, Santa Barbara), this effect might be stronger in girls, because they use omega-3 fats not just to build their brains; they also store them on hips and thighs as preparation for developing the brains of future babies. The researchers found a correlation between the cognitive test scores of 4 000 children aged 6–16 years and their consumption of omega-3 fatty acids – the more they consumed, the higher their scores. Furthermore, omega-3s accounted for twice the improvement in girls as in boys – and girls’ test scores (not boys’) plummeted with increasing consumption of omega-6 fatty acids, which seemed to ‘push out’ the omega-3 in girls. Omega-3s are linked in various studies not only to improved learning and memory, but also to resistance to depression and bipolar disorder, schizophrenia, dementia, attention-deficit disorder, and dyslexia. They are found in oily fish, walnuts, and kiwi fruit, and there seems a strong negative correlation between levels of clinical depression in a country and its fish consumption. In addition,
diets rich in trans- and saturated fatty acids (such as deep-fried foods and butter) can reduce cognitive performance within weeks. Various nutrients power the brain, asserts Fernando Gómez-Pinilla (University of California, Los Angeles) in a review of the literature. Folic acid, for instance, can help those aged 50–70 years to ward off the cognitive decline that accompanies ageing. In a three-year study, Joan Durga and colleagues at Wageningen University in the Netherlands found that people taking such supplements did better in memory tests, information-processing speed, and verbal fluency – so spinach, orange juice, and Marmite (all rich in folic acid) are recommended. Vitamin E (found in vegetable oils, nuts, and green leafy vegetables) has been associated (in mice) with retention of memory into old age, and with longer life. Eating well seems a key to a healthy brain, say the studies – but overeating puts oxidative stress on this all-important organ, and can undermine the good work! Sources: New Scientist, 16 February 2008 and The Economist, 19 July 2008.
Nutrition – you are what you eat No doubt about it – diet and lifestyle affect your health. Here’s why and what to do about it.
From molecules to society Studying nutrition means finding out how people’s health depends on where and how they live and what they eat, explains Esté Vorster, and many scientific disciplines work together to produce answers.
utrition as a branch of knowledge has followed the history of humankind. From ancient times there have been perceptions and teachings that what people ate determined their state of health and risk of disease. This kind of interest is as alive today as it ever was. After the discovery some two centuries ago that limes and oranges could cure scurvy on British naval ships, came investigations into specific nutrients and their physiological effects, followed by a focus on ways to prevent deficiency and disease. Now scientists understand more clearly how environment and lifestyle influence health, as well as what, when, and how much we eat. The prevailing culture, the aggressive marketing of specific products, dietary ‘fashions’, peer pressure, what is available and affordable, and people’s liking for fatty, sugary, and refined foods – all these play a part. Also, individuals are biologically conditioned to respond to diets in different ways. To study the effect of nutrition on health, researchers now have to consider other factors too – sociological, economic, and psychological. Our team’s ‘from molecules to society’ approach reflects a holistic and integrated way of combining different types of investigation to try to understand just what Photographs: Courtesy of the 5-a-Day for Better Health Trust
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makes us eat the things we do in our changing environments, and how diet can affect quality of life. Nutrition transition – from farm to city life The ‘nutrition transition’ is a term globally used to describe changing dietary patterns and effects on health when people move from rural to urban areas, in the process losing traditional practices as they adopt ‘western’ city lifestyles. The changes in eating habits often alter nutritional status, health, and the kinds of disease to which urbanizing individuals and communities succumb. Our THUSA study in the North West province has examined this nutrition transition over the past decade. THUSA – a Setswana word meaning ‘help’ – is an acronym for Transition and Health during Urbanisation of South Africans. In this study, the dietary, nutrient, and alcohol intakes (plus environmental factors, such as stress) of a group of some 1 850 healthy people from different communities were related to their psychological and biological health profiles1. The participants were 15 years and older, included men and women, spanned the socio-economic range, and lived in five different types of community: deep rural, farming, informal housing, former African townships, and fully urbanized professional. Although just from the North West province of South Africa, the group’s ‘transitional’ conditions reflect those found throughout Africa and in other developing countries. THUSA results have reached policymakers, health professionals, other scientists, and participating subjects and communities. Some form the basis of policy2. There were many interesting findings. 1.
With urbanization, for instance, the nutritional status of many of the subjects improved due to an increase of meat, eggs, fish, and milk in their diets, and the mean intake of dietary iron of both men and women improved3. Many people’s micronutrient status was still not optimal, however, because they weren’t eating enough fruit and vegetables (the recommendation is at least 400–500 g, or five servings per day). But the transition from a ‘rural’ diet – consisting mainly of maize as staple, with a limited variety of other foods such as milk, meat (chicken), and marogo (green leafy vegetables) – to a more western diet brought a sharp rise in total fat intake (from about 23% of total energy in rural areas to more than 30% in urban areas). With it came an ‘instant’ risk factor for obesity, diabetes, heart disease, and some cancers (including breast, prostate, and colo-rectal cancers). Another problem in both urban and rural areas was undiagnosed diabetes. About 5% of women, and between 1% and 6% of the men in the study (from rural and urban areas, respectively) were now, for the first time, diagnosed with diabetes. The inference is that African communities have many undiagnosed diabetics, and that there’s a need for screening adult South Africans, so that prevention and treatment programmes can begin. Diabetes can be prevented and controlled in adults through a prudent diet low in fat and rich in legumes (pulses) – such information needs to be widely known.
The participants were all volunteers, who consented to give blood and other biological samples for detailed laboratory study. The fieldwork in 37 randomly selected sites in the North West province took place from 1996 to 1998, and the communities are at present being followed in a 12-year prospective study (2005–2017). 2. For the THUSA-based science behind South Africa’s pioneering Food-Based Dietary Guidelines, see Esté Vorster, “Healthy foods from Mother Earth”, Quest, vol. 4, no. 2 (2008), pp. 44–48. 3. With the move from rural to urban areas, men’s mean intake of dietary iron improved from 7.8 (± 0.42) mg/day (on farms) to 10.8 (± 0.48) mg/day for those following a westernized (urban) lifestyle. For women, the corresponding figures improved from an intake of 7.5 (± 0.33) to 10.4 (± 0.39) mg iron per day.
Hypertension (high blood pressure) was an even greater problem – given the high risk of stroke that it carries, and the fact that it is often undiagnosed and untreated. It can come partly from oversalting the food, in preparation or at the table. High blood pressure can be kept under control very well with modern medicines combined with a sensible, low-salt diet – it is unnecessary for so many people to suffer from it. Overweight and obesity were in evidence, in both urban and rural settings, particularly among women, including older and younger ones. Some 28% of all the women in the study were obese, with body mass indexes of more than 30 kg/m2 (see box on page 18). Obesity was prevalent even in communities that did not always have enough to eat, indicating that low-quality diets in poor families often include large volumes of staple foods. In rural areas, obesity was still often associated with health, wealth, and beauty – so people need to know the health risks of carrying too much weight. Many of the women of child-bearing age were deficient in micronutrients – in particular, they lacked iron and were anaemic. This has serious consequences for future pregnancies, as well as for the babies, who may be at risk of physical and mental underdevelopment. To create a society that has healthy babies and infants growing up with the competence and potential to benefit from education, these micronutrient deficiencies must be addressed. The fortification of maize meal and bread flour in South Africa will help (as legislated subsequent to the results of the THUSA study).
The core business of the North-West University’s Centre of Excellence in Nutrition (CEN) is to research local and global nutritional problems and to build capacity by training postgraduate students. The centre involves itself in projects elsewhere in Africa, as well as outreach activities to improve the nutritional status of vulnerable people, especially in the North West province. Its research provides relevant information and new knowledge addressing nutritional challenges facing South Africa and the world, including malnutrition. Our research clusters around public health nutrition (epidemiological studies), therapeutic nutrition (clinical intervention studies), and basic molecular and genetic studies. Work in the CEN addresses aspects of nutrition that affect society deeply. These include inequity in food security and nutritional status in households, communities, and population groups; issues related to poverty, ignorance, the HIV/AIDS and TB pandemics, and inappropriate survival strategies (including alcohol abuse and violence); persistent undernutrition in children; widespread micronutrient deficiencies; the rise in overweight and obesity; and nutritional aspects of non-communicable diseases such as diabetes, cardiovascular disease, and certain cancers.
The vicious, intergenerational cycle of poverty, under-, and overnutrition UNDERNUTRITION (undernourished pregnant mothers; fetal growth restriction)
Lack of care Unhygienic environments Food insecurity
Low birth-weight babies Undernourished infants
• Growth impairment (underweight; stunting) • Mental underdevelopment • Compromised immune system
Adults with decreased human capital and competence
Increased risk of obesity and other NCDs
Inappropriate breastfeeding and weaning Increased risk of infectious disease
Micronutrient deficiencies (Fe, Zn, Vit. A)
Increased morbidity and mortality
In this cycle, poverty brings food insecurity, lack of education, lack of care, risk of infectious diseases, and undernourished pregnant women and babies in the womb. Poor families (lacking access to safe water, for instance) often cannot care for babies properly. Undernourished babies and infants have restricted physical growth and mental development, becoming adults who may be unable to escape poverty or feed their own families. Furthermore, low birth-weight babies (full-term babies weighing less than 2.5 kg) are ‘metabolically programmed’ for high risk in later life of obesity, hypertension, and diabetes. (Nearly a third of South African children suffer from some form of undernutrition, and almost two-thirds of women are overweight or obese.) Breaking the cycle needs appropriate interventions at critical times – for example, nutritional supplementation or fortification for teenage girls who also, as the mothers of the future, need to be educated to eat enough vegetables and fruit each day, and to avoid too many fast and convenience foods that are loaded with fat, sugar, and salt, with too little dietary fibre and too few micronutrients.
low-fat, micronutrient-rich diet – the kind of diet, containing traditional and indigenous foods, that was at the heart of rural eating cultures. ■ Professor H.H. (Esté) Vorster is the Director of the North-West University’s Centre of Excellence for Nutrition – the only centre of its kind in Africa. Her development of a transdisciplinary approach to nutrition research and practice is supported and taught around the world.
For background about the past read Walter Gratzer, Terrors of the Table: The Curious History of Nutrition (Oxford University Press, 2005). Find out about the transdisciplinary approach to nutrition in M.J. Gibney, H.H. Vorster, and F.J. Kok (eds), Introduction to Human Nutrition (Blackwell Science, Oxford, 2002). Discover THUSA study papers and references by googling the THUSA study (and authors’ names); read the summary by H.H. Vorster et al., “The nutrition and health transition in the North West Province of South Africa: a review of the THUSA (Transition and Health during Urbanisation of South Africans) study”, Public Health Nutrition, vol. 8 (2005), pp.480–490. ▲ ▲
Improving the situation The THUSA study confirmed observations made in some other developing countries – that the nutrition transition means overnutrition of macronutrients (too much fat and refined carbohydrate from cheap fast foods and snacks), with the battle against undernutrition, especially of micronutrients, still to be won. The double burden of nutrition-related diseases is often seen in the same family, with underweight small children contrasting with their overweight mothers or caregivers. What’s needed is nutrition education in the broadest sense, to help everyone to understand their environment from a nutritional point of view, and to know the very real dangers of overindulging in foods suddenly available and affordable in a ‘new’ urban way of life. It’s also useful to learn the value of a prudent,
Nutrition research at North-West University
Quest 4(3) 2008 15
Right: Children with a caregiver at a rural crèche. Photographs: J.C. Jerling unless otherwise stated
Johann C. Jerling explains the importance of getting enough vitamins and minerals in the diet.
Micronutrients for healthy living T oo often, we think only about the volume of food we eat. We don’t want to feel hungry, and when we’re full we assume we’ve been nourished. Seldom do we consider the nutritional quality of what we eat. In talking of the ‘nutritional quality’ of food, we normally think of its protein, carbohydrate, and fat content – that is, the ‘macronutrients’ that have physiological functions and
provide energy. But food quality is also determined by its vitamins and minerals, collectively referred to as ‘micronutrients’, which play an important role in the way the body chemistry works. They are also important for normal growth, resistance to disease, and optimal cognitive and physical performance. The micronutrient composition of foods – therefore the quality of our diet – is
The nutrient composition of three common foods Nutrient
Water Energy Protein Total lipid (fat) Carbohydrate Fibre, total dietary Sugars, total Minerals Calcium (Ca) Iron (Fe) Sodium (Na) Zinc (Zn) Vitamins Vitamin C, total ascorbic acid Thiamin Riboflavin Niacin Vitamin B6 Folate, total Vitamin B12 Vitamin A, IU Vitamin E (alpha-tocopherol) Lipids Fatty acids, total saturated Fatty acids, total monounsaturated Fatty acids, total polyunsaturated Cholesterol
Unit g kJ g g g g g
35.7 1115 10.9 3.6 47.5 3.6 5.75
Value per 100 g 85.6 218 0.26 0.17 13.8 2.4 10.4
Steak (trimmed of visible fat) 59.7 916 29 10.5 0 0 0
mg mg mg mg
142 3.5 521 1.2
6 0.1 1 0.04
19 2 58 5.2
mg mg mg mg mg mcg mcg IU mg
0.2 0.4 0.31 5.2 0.12 85 0 0 0.2
4.6 0.02 0.026 0.09 0.04 3 0 54 0.2
0 0.07 0.13 8 0.58 9 1.9 0 0.4
g g g mg
0.8 0.8 1.4 0
0.03 0.007 0.05 0
4.1 4.3 0.4 79
Source: US Department of Agriculture, Agricultural Research Service, USDA National Nutrient Database for Standard Reference, Release 20 (2007). Available at the Nutrient Data Laboratory home page, www.ars.usda.gov/ba/bhnrc/ndl
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largely determined by their chemical composition. There are also other things that influence food quality, such as food production practices, as well as processing, storage, and preparation in the home. It’s often debated, for example, whether or not fresh vegetables are healthier than frozen ones. The vitamin C and flavonoid content of vegetables deteriorates on the shelves of grocery stores; for this reason, in some cases, frozen vegetables might be more nutritious than fresh ones. We also know that some vitamins are sensitive to heat, and can be destroyed during food-processing and home cooking. In much of Africa, grains are often germinated before being dried and pounded into flour. During the germination process, phytate (the main form in which phosphorus is stored in plants) is metabolized. Phytates are also powerful inhibitors of divalent metal absorption, so lowering phytate content by processing grains in this way improves the nutritional quality of these staples. Why all the fuss about nutrients that we need in such tiny amounts? The fact is that 30% of children in southern Africa under the age of five years are too short for their age and 11% are underweight. These conditions are directly caused by malnutrition. Vitamin A deficiency, iron deficiency, and zinc deficiency are widely prevalent across the region and contribute to death and disability, not just in young children but in adults as well. The high human and economic cost of micronutrient deficiencies is a major contributor to underdevelopment on the African continent. In 2002, nutritional deficiencies in South Africa were directly responsible for the loss of 443 000 Disability Adjusted Life Years (DALYs) per year1 (or years of ‘healthy’ life lost).
Left: Mealtime at the crèche. Photograph: H.S. Kruger
Right (from top): A child eating porridge made from fortified maize. Laboratory analysis of samples. Volunteers taking part in the study on bioavailability of iron compounds.
Iron rations Our research group has a specific interest in the bioavailability of micronutrients (that is, how much of them the body actually absorbs and uses). One strategy for alleviating micronutrient malnutrition is to fortify widely consumed staple foods with vitamins and minerals. Widespread micronutrient malnutrition in South Africa led to regulations being passed that made it mandatory to fortify all maize and wheat flour with a standard mix of micronutrients, including vitamin A, thiamine, riboflavin, niacin, piridoxine, folic acid, iron, and zinc. The idea was to fortify these products in a way that would substantially benefit the general population at the present level of flour consumption. The Recommended Dietary Allowance (RDA) was used as a benchmark, and maize and wheat flour is fortified to a level where one could expect around 20–30% of the RDA to be provided by bread and maize flour. These micronutrients are added in a specific form, for example zinc oxide, vitamin A palmitate, or electrolytic iron. According to their unique chemical composition, some compounds may be better absorbed and utilized by the body, so using less of them would have the same benefit but might be cheaper, or might have benefits in terms of the taste or colour of the fortified flour. The main concern is that whatever is added should end up in the body and play a physiological role2. Because the iron compound currently used as a mandatory fortificant is only to a very small extent utilized by the body, we decided to investigate the bioavailability of two alternative iron compounds
– iron fumarate and iron EDTA. Our investigations used sophisticated stable isotope technology in collaboration with Dave Hilmers (a former NASA astronaut) from Baylor Medical College (Houston, Texas), and Lena Davidsson from the International Atomic Energy Agency (Vienna, Austria). Stable isotopes make it possible to track the biological path of specific iron atoms within the body, letting us know exactly what happened to stable iron isotopes that were consumed as part of a mixed meal. The programme is a unique blend of mathematics, physics, chemistry, pharmacology, and nutrition. Stable isotopes (that is, not radioactive ones) of the same element differ in mass but have the same chemical properties and therefore behave almost identically under physiological conditions in the body. The differences in mass are due to differences in the number of neutrons. The element iron has four stable isotopes and the natural abundance (that is, the relative proportions in nature) of each is as follows: 54Fe (5.85%); 56Fe (91.75%); 57Fe (2.12%); and 58Fe (0.28%). Technically, it is possible to make metallic iron that contains high proportions of a particular isotope, and to use that iron to synthesize the desired compound to be tested. Doing this allowed us to determine accurately just how much iron was absorbed from each compound, in a group of children with marginal iron status, by measuring how much iron was incorporated into their red blood cells over a 16-day period. The main outcome of the study was that either of the compounds could be used to replace electrolytic iron in maize flour,
1. The DALY is a health-gap measure that extends the concept of potential years of life lost due to premature death, to include equivalent years of ‘healthy’ life lost through poor health or disability. The DALY combines in one measure the time lived with disability and the time lost due to premature mortality. One DALY can be thought of as one year lost of ‘healthy’ life, and the burden of disease as a measure of the gap between current health status and an ideal situation where everyone lives into old age free of disease and disability. (Source: WHO Global Burden of Disease Estimates, 2002.) 2. The following foods are the most common sources of dietary iron: chicken liver and beef and other red meat (haem iron from animal sources is more easily absorbed); dried beans, dried fruits, iron-fortified cereals, and whole grains such as wheat and oats (non-haem iron from plants is less easily absorbed).
so the decision would be based on cost and on the compound’s effect on the colour and taste of the flour. At present, iron EDTA is more expensive than iron fumarate – but its advantage is that it has less effect on the taste and colour of maize and wheat flour. Iron deficiency has long been associated with developmental processes in infants and young children. Studies consistently indicate that children who are anaemic owing to lack of iron in early childhood continue to have difficulty with cognitive and motor development as well as school achievement into middle childhood. This is just one area of micronutrient deficiency that, when successfully addressed, can change people’s lives.
Professor Jerling (Faculty of Health Sciences, and CEN, North-West University) has worked in the field of iron bioavailability for five years. He was instrumental in establishing the expertise to use stable isotope technology in nutritional studies at the university – the only group in South Africa equipped to do so. For further information, visit www.sightandlife.org and www.idpas.org.
Quest 4(3) 2008 17
Hattie Wright and Salome Kruger explain how nutrition and physical activity – interrelated in so many ways – are integral to health, well-being, and keeping body weight under control.
Eating and exercise T
he attractions of television and the internet are making people, young and old, less inclined to exercise. This is a worldwide concern. But combining healthy nutrition with regular daily physical activity helps people both to lose weight and to maintain a healthy body weight, which is normally defined by a person’s body mass index. Over the past few decades, obesity has increased to epidemic proportions, in adults as well as children. In 2007, the World Health Organization estimated that over a billion adults worldwide are overweight and at least 300 million of these are obese1. Furthermore, an estimated 22 million of the world’s children under the age of five years are overweight or obese. Being overweight or obese increases the possibility of developing noncommunicable diseases, including diabetes, cardiovascular disease (such as hypertension, From top: Rugby practice (top and middle) Photographs: J.C. Jerling
Youngsters taking part in the PLAY physical activity programme in a township school. Photograph: H.H. Wright and H.S. Kruger
Body Mass Index Your body mass index (BMI) tells you if your body weight is healthy. To calculate your BMI, divide your current weight by your height squared. For example, if you weigh 60 kg and you are 1.68 m tall: 60/1.68² = 21.26. A result between 18.5 and 24.9 is considered healthy; below 18.5 is classified as ‘underweight’; 25–30 as ‘overweight’; and above 30 as ‘obese’. Athletes with a lot of muscle mass but a low proportion of body fat may have a BMI above 25, which for them is still healthy – so it’s important to use this index with care.
congestive heart failure, strokes, atherosclerosis, and coronary heart disease), and certain types of cancer. The risk of unwanted weight-gain rises through sedentary behaviour (such as watching television, playing video games, and spending hours at the computer), decreased physical activity (less manual labour, less exercise), low level of education and socio-economic status, urbanization (the move from rural to urban life in developing countries), and increased energy (kilojoules) and fat in the diet. Improving South Africa’s health, then, means trying to understand as far as possible the interaction in various communities between the food they eat and the physical activity they engage in. Food in an athlete’s life Nutrition is critical for physically active people, such as athletes – and optimal nutrition improves sports performance. Nutrition during training as well as on competition days has been well researched and, depending on an individual’s needs, specific ways can be recommended to improve sports performance. Athletes following a poor diet or a diet low in nutrients undermine their chances of success. They should follow South Africa’s Food-Based Dietary Guidelines for a healthy diet. They should eat three main meals a day as well as healthy snacks between meals. Every day, to replace the fluid they lose
through sweating, they must consume water and sports drinks, especially in hot and humid weather. Female athletes should take special care to get sufficient calcium and iron by including milk and dairy products (for calcium) and animal products (for iron). Without the daily recommended levels of these nutrients (that is, 1 200 mg of calcium, and 18 mg of iron), they risk poor bone health or anaemia, which can not only reduce sports performance but also affect growth in children and adolescents. Not following a healthy diet can result in physical problems such as low bone density, low blood-sugar levels, decreased mental function, poor hand-eye coordination, overtraining syndrome, and fatigue in the early stages of a competition. Athletes therefore need healthy foods to ensure that their muscles and the rest of their bodies get all the nutrients needed for top performance. Intensifying a training programme increases the need for energy, so that’s when athletes need to eat more than normal. They can make the size of their portions bigger, especially of foods high in carbohydrates. To make sure they have enough energy and nutrients, they can also snack more, or more often – on healthy food such as fresh or dried fruit, yogurt, cereal bars, sandwiches, pure fruit juice, bran muffins, popcorn, and mealreplacement supplements/shakes.
1. For this World Health Organization analysis, visit www.who.int/dietphysicalactivity/publications/facts/obesity/en
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Guide to healthy living Our CEN studies have produced some practical guidelines and recommendations. For improved quality of life ■ Be physically active for 50 minutes a day, most days of the week ■ Choose healthy between-meal snacks (for example, fresh fruit, low-fat bran muffins, popcorn) ■ Avoid high-fat foods and snacks ■ Limit fats and oils in meal preparation ■ Eat regularly throughout the day, especially at breakfast-time ■ Don’t skip meals ■ Drink 4–6 glasses of clean, safe water daily ■ Limit sedentary free-time activities (such as watching TV and playing computer games) to two hours a day ■ If you work at a computer all day, take short ‘exercise’ breaks – walk briskly at lunchtime, take stairs instead of the elevator, walk quickly to fetch or deliver work to colleagues instead of using internal mail, and do ‘deskercises’ at least once a day to stretch and move your legs and arms. For improved sports performance ■ Base your meals and snacks on carbohydrate-rich foods ■ Eat regularly throughout the day and don’t skip meals ■ Replace fluid losses daily, to avoid dehydration ■ Increase food intake when training increases ■ Focus on high-glycaemic-index carbohydrate foods during training or competitions (for example, sports drinks, jelly-type sweets, ripe bananas, white bread with jam) ■ After training/competing, have a high-carbohydrate food with some protein within 30 minutes, to replace and repair body stores (for example, a sandwich with low-fat meat filling, yogurt and fresh fruit, maize porridge with milk).
Keeping active Our CEN research team focuses on aspects of nutrition connected with physical activity. We investigate ways to improve sports performance with the help of the right kind of diet, and we study the effects of nutrition and other lifestyle factors on the health of athletes. We have also been examining factors contributing to obesity among South Africans, as well as nutrition interventions (including physical activity) to prevent or treat it. The THUSA study (see pages 14–15) and the 2000–2001 THUSA BANA (bana is the Setswana word for children) were two projects during which we investigated the prevalence of obesity in black, Tswana-speaking South African adults (aged 15–70 years) and children (aged 10–15 years) in the North West province. We found that physical inactivity was an important determinant of obesity, and was also associated with increased risk of cardiovascular disease among adult women. Furthermore, it was related to overweight among 10–15-year-old girls. Both studies recommended the creation of opportunities for enjoyable recreational physical activity and sport participation, in particular for girls and women. In another study – called PLAY (for PhysicaL Activity in Youth) – which we conducted in 2004–2005, we implemented a physical activity programme in township high schools so as to improve strength and lean body weight in the children. The intervention included aerobics with music, ball games, and strength
exercises. After six months, the children who took part had, on average, about 3% less body fat and about 1.5 kg more lean mass than a control group that did not participate. During the study, we also identified some of the obstacles preventing the children from participating in afterschool activity programmes, such as having to take care of younger siblings and do household chores. The implication is that it’s preferable for physical activity to be introduced as part of the normal school day in the curriculum, rather than after school hours. Studies such as these can provide practical guidelines on how people in different circumstances can adjust, to bring more physical activity into their lifestyles – and keep themselves fit and healthy for years to come. ■
H.S. Kruger, C.S. Venter, & H.H. Vorster, ”Physical inactivity as a risk factor for cardiovascular disease in communities undergoing the rural to urban transition: the THUSA study”, Cardiovascular Journal of South Africa, vol. 14 (2003), pp.16–23; and R. Kruger, H.S. Kruger, and U.E. MacIntyre, “The determinants of overweight and obesity among 10- to 15-year-old schoolchildren in the North West Province, South Africa – the THUSA BANA study”, Public Health Nutrition, vol. 9 (2006), pp.351–358.
Both authors are based at North-West University (Potchefstroom Campus). Dr Wright is a registered dietician who specializes in sports nutrition and advises provincial and national athletes and teams about nutrition for optimal performance. Amongst other things, Professor H. Salome Kruger is involved in community nutrition and public health nutrition. For more on keeping healthy, visit www.mrc. ac.za/chronic/healthykids; www.intelihealth. com/IH/ihtIH/E/9273/8254.html; and (for ‘deskercises’) http://uclivingwell.ucop.edu/ deskercise/legs.html. For sports nutrition, read G. Steenkamp & L. Delport, Eating for Sustained Energy (Tafelberg, Cape Town, 2004); C. Fuller & S. Meltzer, Eating for Sport (Struik, Cape Town, 2005); and visit www.sportsdietitians.com.au/. For CEN research on overweight and obesity, read H.S. Kruger, C.S. Venter, H.H. Vorster, & B.M. Margetts, “Physical inactivity is the major determinant of obesity in black women in the North West Province, South Africa: the THUSA Study”, Nutrition, vol. 18 (2002), pp.422–427;
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Right: The haemostatic system (the system in the body that causes blood to clot and the clotted blood to be broken down again) consists of four parts: the endothelium, which is the blood-vessel wall; blood platelets (fragments of larger cells, megacaryocytes, that play an important role in blood clotting); coagulation proteins (such as thrombin and fibrinogen) circulating in the blood; and the fibrinolytic system, responsible for breaking down formed blood clots, once the damaged vessel wall has been restored. Fibrin is the mesh of fibres that captures platelets and blood cells to cover and seal damaged blood vessels; plasminogen is the inactive precursor of plasmin, the protein responsible for breaking down the fibrin network. Tissue plasminogen activator (tPA) is the protein that activates plasminogen to plasmin; plasminogen activator inhibitor 1 (PAI-1) is the protein that inhibits tPA; and D-Dimer is the product of fibrin degradation by plasmin. Diagram: J.C. Jerling
Endothelium Plasma protein clotting system
How blood clots form & disintegrate Marlien Pieters considers blood-clotting mechanisms at a complex molecular level – and explores some implications for diabetic patients.
he flow of blood through the body keeps people alive and functioning. Under some conditions, however, blood thickens and turns semisolid, forming a clot. This process prevents us from bleeding to death when we have a cut or open wound – instead of flowing, the blood forms a thick lump at the site of the injury, sealing the wound and stopping the bleeding. In normal circumstances, the human body prevents blood from clotting in the veins and arteries. But if the wall of a blood vessel carrying the blood is damaged, clotting (also called coagulation or haemostasis1) is activated to prevent uncontrolled bleeding. In a healthy individual, there is a balance between clot formation and breakdown. But in people with bleeding tendencies, the balance has shifted towards breakdown (fibrinolysis2) and, as often happens in cardiovascular disease, towards clot formation, which can narrow or block blood vessels. Disease conditions associated with increased blood-clot formation include diabetes, stroke3, deep-vein thrombosis, and coronary artery disease – from the narrowing
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of the blood vessels around the heart (angina) to complete occlusion of blood vessels around the heart (heart attack). In general, though not exclusively, cardiovascular disease is age-related. It is observed more frequently in older people, probably because of continued long-term exposure to triggers or causes, such as high-fat-saturated diets, smoking, obesity, inactivity, and stress. South Africa also has other vulnerable groups of people. Among the country’s black population, there is an alarmingly high prevalence of hypertension (a factor causing occlusive stroke, and potentially haemorrhagic1 stroke) and of strokes. In 2000, the age-standardized mortality rates were 145 per 100 000 of the population for men, and 160 for women. There has been a recent increase in cardiovascular disease in this population group in urban areas, probably resulting from the nutrition and health transition that normally accompanies the move to town. In addition, the Indian community suffers from a particularly high prevalence of type 2 diabetes mellitus.
Such information indicates the importance of understanding the haemostatic profile4 of different South African population groups and how dietary habits might have an influence. Our research team is one of only a few worldwide that investigates the relationship between diet and blood clotting. Through thick and thin Our special interest in haemostasis – the mechanism by which bleeding is stopped – began in the late 1980s when it was observed, in different animal model studies, that the blood of animals fed a high-fibre diet took longer to clot than the blood of animals fed a control diet. In the early 1990s, we started focusing on the structure–function relationship of haemostatic proteins – that is, on how the structure of a molecule influences its function. When blood clots, the final coagulation protein that is activated in the process is fibrinogen. Once that happens, the molecules bind to each other to form a mesh of long fibrin fibres, which captures platelets and blood cells to form a plug for covering
1. The prefix haem- comes from the Greek word for ‘blood’: ‘haemostasis’, then, means ‘the stopping of blood circulation’, and ‘haemorrhage’ means ‘profuse bleeding from ruptured blood vessels’. (Collins English Dictionary) 2. The combining form -lysis comes from the Greek word for ‘loosening’, and indicates a dissolving or loosening or breakdown process. 3. Increased blood clot formation increases the risk of occluding stroke. Occluding stroke is stroke caused by blockage of blood vessels in the brain due to the clotting of blood; haemorrhagic stroke is caused by excessive bleeding from blood vessels in the brain. 4. Many different proteins are involved in the haemostatic system. The term ‘haemostatic profile’ is used to describe the mean concentrations and activities of the different proteins involved both in the clotting of blood and the breakdown of blood clots that have already been formed. Thirteen clotting factors (proteins) are involved, plus co-factors associated with the process. On the opposite side is the haemolytic system (breakdown of blood clots), comprising several more factors. Normally, studies of nutrition in this context investigate the concentration/activity of selected proteins in the haemostatic system, which does not necessarily give an overall indication of increased clotting or breakdown, but rather the effects of a specific nutrient on the concentration/activity of each selected protein. At this stage, therefore, it is difficult to predict the overall clotting potential of a nutrient or food. We can assess the effect of a food/nutrient on an individual protein in the haemostatic profile, but not yet whether, clinically, it will increase clotting. We do know that certain haemostatic proteins are known risk markers for cardiovascular disease, so if the diet can reduce these, it could also decrease cardiovascular disease.
Left: Scanning electron microscope (SEM) image of a fibrin network containing platelet aggregates (A). Source: E. Pretorius et al., “Ultrastructural comparison of the morphology of three different platelet and fibrin fibre preparations”, The Anatomical Record, vol. 290 (2007), pp. 188–198
Right and below: Successive confocal microscope images of a fibrin clot (fibres shown in green, 60x magnification in the microscope). The clot is being digested at the lysis front, which here is shown advancing from right to left in the lower image. The second image was taken 6 minutes after the first.
the damaged blood-vessel wall. For the past two decades or so, it has become evident that these fibrin fibre structures can vary from long, thin, tightly intertwined fibres to thicker fibres with larger pores in the fibre mesh. This variation in the fibrin network is important in shifting the delicate balance between the formation of a clot, on the one hand, and its breakdown (lysis) on the other. In general, fibrin clots that have thinner fibres, more branch points, and smaller intrinsic pores tend to be more dense and resistant to lysis, thereby contributing to the risk of thrombosis5. In researching the structure–function relationship of fibrinogen, we use a method that determines the speed with which a solution passes through it. We start with human plasma in a cuvette, and add clotting activators to cause the blood to clot. We then pour a special solution over the clot, allowing the liquid to flow out of the cuvette through an opening at the bottom, and we measure the rate at which it permeates the clot. This rate indicates how easily the blood clot can be broken down by lytic agents (substances that cause clots to disintegrate – some occur naturally in the blood; others are given through medication). The speed at which they move through the clot helps to determine the rate at which clots can be dissolved – the faster the permeation, the quicker the breakdown of the clot will be. The sizes of the pores in a blood clot contribute partly to the speed at which lytic agents can move through it. In our investigations, we also
measure the speed at which the clot forms; the diameters and densities of its fibres; its mechanical properties (including elasticity and rigidity), which may help us to understand whether or not it will break up or deform under stress, caused, for instance, by blood flow; and the rate at which it is broken down or dissolved. To determine a clot’s average fibre diameter and density, we use scanning electron microscopy (SEM), which magnifies the fibres up to 10 000 times. To measure the lysis rate, we use confocal microscopy, which magnifies fibres up to 60 times and allows us to follow the breakdown process over time. Practical and useful This kind of investigation has practical benefits. When blood clots form and are not broken down, the result may be a deep-vein thrombosis, a lung embolism, heart attack, or a stroke (depending on the clot’s location in the body). Lytic agents are used to dissolve the clots. So a technique for measuring the speed with which a specific lytic agent breaks a clot down can reveal something about a particular agent’s lytic ability, or offer information about the structure of the fibrin network – it could, in future, answer the question as to whether a specific patient’s blood clots are easy or difficult to lyse, which in turn could predict his or her risk of cardiovascular disease. It’s to answer such questions that we conduct our research – and we keep making progress. One of our recent projects was to determine the fibrin network structure of black South African type 2 diabetic patients, because they often develop complications related to increased
5. Thrombosis is the formation of a thrombus – a clot of coagulated blood that forms within a blood vessel or inside the heart and remains there, often impeding the flow of blood. 6. When a doctor tells a diabetic patient that his or her blood glucose levels are ‘controlled’, it means that the blood glucose levels are comparable to normal blood glucose levels (considered to be under control); when the blood glucose levels are higher, they are called ‘uncontrolled’. It is, of course, not really the blood glucose levels that are controlled or uncontrolled, but the diabetes itself.
blood-clot formation. We wanted to know if the continuous high levels of blood glucose in uncontrolled diabetes affected a patient’s fibrin network structure through the binding of the glucose to the fibrinogen molecule. We did indeed find that significantly more glucose was bound to the fibrinogen of diabetic patients when their blood glucose levels were uncontrolled than when these levels were controlled6. We also found that when blood glucose levels were controlled, the fibrin network structure improved (in other words, the clots became more permeable and were lysed faster). One of the aims of our work is to help communities to improve their overall health status. Even as we investigate the relationships between diet and haemostasis on a molecular level, we are aware that, further down the line, what we discover can provide guidelines for practical implementation. ■ Dr Pieters, in the Faculty of Health Sciences, North-West University (Potchefstroom Campus), is a senior subject specialist in basic molecular science. Her work focuses on fibrinogen and fibrin network structure and investigating haemostatic profiles of different populations in clinical trials. For details read D.M. Monroe and M. Hoffman, “What does it take to make the perfect clot?” Arteriosclerosis Thrombosis and Vascular Biology, vol. 26 (2006), pp.41–48; and R.W. Colman et al. (eds), Haemostasis and Thrombosis: Basic Principles and Clinical Practice (A. Wolters Kluwer, Philadelphia, 4th ed. 2001).
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Nutrition makes a difference to children infected with HIV/AIDS, explains Salome Kruger. They are far more likely to respond well if good nourishment forms part of their treatment.
Treating children with HIV/AIDS T he number of children infected with the human immunodeficiency virus (HIV) in South Africa during 2005 was estimated to be 240 000. After analyzing death-certificate data, a team from the Medical Research Council concluded that 40 727 children younger than five years died of diseases related to acquired immune deficiency syndrome (AIDS) during a one-year period from 2000–2001, and that this was the most significant cause of death among children in this age range1. Undernutrition and HIV/AIDS act in a vicious cycle – malnourished children with HIV/AIDS are more severely affected by any disease, and more likely to die, than HIV-infected children who are properly fed.
ART and growth The antiretroviral (ARV) drug combinations used at present have been available for about ten years. In April 2004, with the implementation of the South African Comprehensive HIV/AIDS Care Management and Treatment Plan, antiretroviral therapy (ART) became available to children free of charge at pediatric clinics. It includes multivitamin syrup and fortified porridge for underweight HIV-infected children and for those who do not gain weight satisfactorily. Dieticians, nutrition counsellors, and nurses give nutrition education to caregivers. Numerous studies have shown that children with AIDS who receive ART gain more weight, live longer, and suffer fewer secondary infections than those who don’t. Although there are not many published studies focusing on comprehensive treatment of children, the
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results we have indicate that medication and nutritional support seem to work in synergy, with optimal nutrition helping the ART to decrease viral load more quickly. The effect of ART on body composition had been studied in adults. The progressive, selective wasting of fat from just below the skin of the face and limbs (subcutaneous fat) of HIV-infected patients treated with ARVs is known, but few data are available as to how HIV or ART affect body composition in children. What we do know is that all HIVinfected children are at high risk of malnutrition, particularly those living in poverty, and the fact that they are still developing means that (like all growing children) they have additional nutritional needs. Malnutrition retards their growth, makes them more susceptible to infection, and reduces their ability to function – for instance, to walk, run, or work. It can also impair neural development and cognitive function. To examine the effects of ART on these young patients, our research team studied the growth and physical development of HIV-infected children undergoing treatment at a pediatric immunology clinic in Johannesburg. Building on results of studies elsewhere in the world, we wanted to assess their body composition, monitor changes in body composition, and examine their ‘nutritional risk’ – that is, to what extent a very thin child is at risk of disease
owing to poor nutritional status. The team conducting an earlier study in the USA reported in 20062 that 48 weeks of treatment had improved growth and body composition dramatically in HIV-infected children. Previously, in 2002, Dutch scientists had found that ART benefited the growth of HIV-1–infected children, with favourable height and weight in those whose viral load3 had been reduced to at least 1.5 log or to <500 copies/µl4. The increase in body mass index (BMI) (see box on page 18) was greater in children who had started ARV treatment at an advanced stage of infection and a poor nutritional status, than in children whose nutritional status was better at the beginning of treatment. Progressive wasting of subcutaneous fat, accumulation of fat around the torso, high levels of fat (lipids) in the blood, and insulin resistance in HIVinfected patients on ART have been attributed to the long-term toxicity of the drugs used5. Some seem to predispose adult individuals to slowly progressive loss of fat in the limbs, and this loss is markedly accelerated with certain drug combinations. Unlike the adults, who lose fat in the limbs, however, the children on ART generally gained weight, though concerns were raised that weight-gain may be excessive, and perhaps represent a gain in fat rather than lean muscle mass2,4. In our ongoing Johannesburg study of the body composition of children on ARVs, we are using the affordable
1. See P. Groenewald et al., “Identifying deaths from AIDS in South Africa: an update”, AIDS, vol. 19 (2005), pp. 744–745. 2. C. Chantry et al., “Growth and body composition in children beginning or changing antiretroviral therapy”, (Abstract MOAB 0404) XVI International AIDS Conference, Toronto, 13–18 August 2006. (A report on the Pediatric AIDS Clinical Trials Group study 1010.) 3. Viral load (expressed as a concentration) represents the total burden of the virus; the CD4 count represents the concentration of T-cells in the body fighting the virus. If the viral load is high, the CD4 count is low, and vice versa. 4. G. Verweel et al., “Treatment with highly active antiretroviral therapy in human immunodeficiency virus Type 1infected children is associated with a sustained effect on growth”, Journal of Paediatrics, vol. 109 (2) (2002), E25. 5. L. Aurpibul et al., “Lipodystrophy and metabolic changes in HIV-infected children on non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy”, Antiviral Therapy, vol. 12 (2007), pp. 1247–1254.
and non-invasive method of anthropometry to measure changes in growth and development6. The data include serial measurements of height (or length) and weight, with a calculation of BMI, all plotted on growth charts. We take such readings initially at 2- to 3-monthly intervals and, when the patient is stabilized on ART, at 6-monthly intervals. Mid-upper-arm circumference and the mid-arm muscle area in children older than one year give an indication of lean body-mass stores, whereas fat stores in the body are indicated by skinfolds on the back (beneath the tip of the shoulder bone), and at the back of the upper arm. The thickness of the skinfold on the back gives an indication of fat on the torso, and thickness of the upper-arm skinfold shows the measure of fat on the limbs. Changes in waist circumference, as well as waist:hip ratio, are measured to detect fat accumulation over the body’s large internal organs (particularly the abdominal ones) over time. Such fat accumulation is generally associated with an increased risk of cardiovascular disease later in life. Various studies have shown that greater waist circumference was associated with higher blood pressure and blood lipids, even in children7, so monitoring changes in waist circumference in children on ART can help – in anticipation of problems later in life – to identify those with an increased risk of cardiovascular disease, and to initiate dietary and physical activity measures to reduce that risk. Nutritional history and a child’s future A child’s nutritional history also plays a part. In previous studies, our group found that chronically undernourished children had a greater risk of accumulating fat during adolescence than children who were not undernourished8. Undernourished children from low-income groups, therefore, are not immune to becoming overweight, and previously undernourished children may have a greater risk of developing excess weight when they grow up in environments where sufficient food is available. Similarly, HIV-infected children who receive ART and food supplements may risk becoming overweight and developing cardiovascular disease, unless their growth and physical development are monitored as part of the comprehensive treatment of their disease. Their caregivers should include legumes, fruit, and vegetables in the children’s diets, and fats and sugar should be eaten in moderation to prevent excessive weight gain and overweight later, during adolescence and adulthood. ■ Professor H. Salome Kruger is at North-West University (Potchefstroom Campus). She is involved in research on child health, specializing in childhood growth and development as well as prevention of non-communicable diseases. Find useful information in Nutritional care for people living with HIV and AIDS: Answers to frequently asked questions (Department of Health, Pretoria, 2007), available from the Pretoria or provincial offices of the Department of Health; “Guidelines for the management of HIV-infected children” (2005), available at www.doh.gov.za/docs/index.html; and (especially for people newly diagnosed with HIV and their family members) visit the following website www.cdc.gov/hiv/resources/brochures/livingwithhiv.htm. 6. International studies have shown that lean body-mass changes, as measured by anthropometry, agree reasonably well with lean body-mass changes measured by more sophisticated, but expensive, methods such as dual X-ray absorptiometry (DXA), in patients with HIV infection. For more, see S. Chomtho et al., “Evaluation of arm anthropometry for assessing pediatric body composition: evidence from healthy and sick children”, Pediatric Research, vol. 59 (2006), pp. 860–865. 7. S. Caprio et al., “Fat distribution and cardiovascular risk factors in obese adolescent girls: importance of the intra-abdominal fat depot”, American Journal of Clinical Nutrition, vol. 64 (1996), pp. 12–17. 8. H.S. Kruger et al., “Evidence for relatively greater subcutaneous fat deposition in stunted girls in the North West Province, South Africa, as compared with non-stunted girls”, Nutrition: The International Journal of Applied and Basic Nutritional Sciences, vol. 20 (2004), pp. 564–569.
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News Q Energy options
How smoke affects cloud cover and climate
Each year, electricity generation provides 18 000 terawatthours of energy (about 40% of humanity’s total energy use) – a thousandth of a terawatt is the output of a fairly large power station – and emits more than 10 gigatonnes of carbon dioxide. Yet a wide range of carbon-free technologies exist that can generate electricity. They need scaling up to serve the needs of ever-growing populations, and developed in ways that avoid unintended and damaging consequences. An overview in Nature (14 August 2008) gives the pros and cons of various carbon-free options, and offers a verdict on each. Hydropower is popular, in a world that already has 45 000 large dams and many more smaller ones. Hydroelectric power plants currently supply about onefifth of the world’s supply of electricity. Their advantage is that they do not need fuel, but not all regions have the necessary resources. Furthermore, there are adverse ecological effects on ecosystems upstream and downstream, and dams cause barriers for migrating fish. Nuclear fission remains controversial. It is constrained by fuel stocks, but fuel costs are relatively low. The main issues are that there’s no agreed solution to the problem of dealing with the waste generated in nuclear plants over the past half-century; the spread of nuclear power is hard to disentangle from nuclear weapon capabilities; the Chernobyl meltdown caused grave concern as to possible dangers in future; and nuclear power stations could be a terrorist target. Biomass burning is second only to fossil fuels as an energy source. The greatest problem is finding reliable feedstock that is locally available and that does not need to be transported over significant distances. In addition, converting land to the production of biofuels might not be desirable or politically feasible, as there is only so much land in the world, and it’s needed to feed growing populations. Wind power is expanding, and global capacity has risen by nearly 25% in each of the past five years. Its great advantage lies in its not needing fuel, but its use depends on what wind is available, and many people have a preference for turbine-free environments. Geothermal energy depends on the heat from the Earth’s interior, which is difficult to tap (because rock is a poor conductor of heat) except in places where the heat escapes easily – where there are abundant hot springs, for instance. Because high-grade resources are rare, only five countries generate more than 15% of their energy in this way. Without spectacular technological improvements, capacity is unlikely to outstrip that of the hydro and wind options. Oceans provide two types of kinetic energy – from the tides and the waves – but neither at present contributes significantly to the world’s electricity generation, and most technologies for capturing wave power remain firmly in the testing phase. Advantages include the predictability of tides, and waves are more constant than winds, but available resources vary greatly with geography. The verdict is that this form of energy is marginal on the global scale. Solar energy has developed substantially over the past five years, but the amount of electricity that’s generated remains low, even though solar cells are getting cheaper and the technology is improving all the time. The Sun represents an effectively unlimited supply of fuel that costs nothing, and the public on the whole approves of this option. The main limitation is absence of Sun at night and in cloudy conditions, and a further one is the difficulty of storage. But, in the middle to long term, the size of the resource and the potential for developing the technology further make solar power probably the most promising carbon-free technology.
A new study by researchers at NASA and other institutions (published in Science in August) have found a way to improve the ability to predict whether aerosols will increase or decrease cloud cover. They examined aerosols during the dry season in the Amazon valley, when the only ones of any magnitude are from smoke emerging from humaninitiated fires. The evidence enabled them to link the effect of human activity on climate change by way of anthropogenic aerosols, says a co-author of the study, During the dry season, smoke covers wide swathes of the NASA’s Lorraine Remer. Amazon. Isolated towers of cumulus clouds poke through Aerosols are the tiny particles the dense layer of smoke in this photograph taken from an that make up smoke, dust, and airplane in 2005. Photograph: Ilan Koren, Weismann Instutute ocean spray. As they travel with an analytical model that combined knowledge the wind through the atmosphere, of cloud development, satellite observations, they become individually encased by water, and mathematical calculations of aerosol and turn into the droplets that combine concentration and cloud properties, to try to to create clouds. The larger the number of explain how the two effects of aerosols on aerosol particles suspended in air, the larger clouds could influence cloud coverage. the number of small droplets. The smaller Aerosol and cloud observations along the the droplets, the longer it takes for a cloud Amazon during the 2005 dry season gave to produce rain. Such clouds produce less details of what happened, in stable weather rainfall, last longer, and create more conditions, when there was an abundance of cloud cover. aerosols caused specifically by fires that people Another effect of aerosols on clouds is had started to help them to clear new land and their ability to absorb heat from the Sun. prepare old pastures for the next crop season. This process warms the atmospheric layer, Co-author of the study, J. Vanderlei and changes the environment in which the Martins (University of Maryland, Baltimore, cloud develops into a less hospitable one for USA), summarized the findings. “As we’d cloud growth. Even the smallest changes in expected in applying our model, increased cloud cover can significantly warm or cool the smoke from the fires created clouds rife with atmosphere and affect rainfall in the region. a more pronounced radiative effect – rich Knowing from previous investigations that with human-caused aerosols that absorbed aerosols play an essential role in the way that sunlight, warmed the local atmosphere, and clouds develop, the researchers explored the blocked evaporation. This led to reduced connection between a change in the amount cloud cover over the Amazon.” The team of human-caused aerosols and change in were encouraged that the science behind the structure of clouds. They had noted the model had been verified, and that the that increased aerosols over the Amazon model would apply in other regions as well. produced less cloud cover, but that increased aerosols over the Atlantic Ocean actually Sourced from www.nasa.gov. produced more cloud cover. They developed
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Fact and fiction Reading fiction can help us to negotiate the difficulties of the social world more effectively, asserts psychologist Keith Oakley. He and his colleagues at the University of Toronto, Canada, have for the first time put together scientific evidence (published in the Review of General Psychology) that reveals the life-enhancing benefits of reading fiction. Oakley proposes that fiction works as a simulator, improving people’s social skills much as a flight simulator improves a pilot’s skills. To test the idea, the researchers ran an assessment of the amount of fiction – as distinct from non-fiction – read by the subjects in their study. The subjects then did a series of exercises, including a ‘mind-in-the-eyes’ test, which measures empathy and social acumen. Participants looking at photos of people’s eyes, as if seen through a letterbox, have to choose the most appropriate of four given words to describe what the person in the photo is feeling (for example, “joking”, “amused”, “insistent”, and “relaxed”). Fiction readers were found to have substantially greater empathy as measured by this test, and also performed somewhat better on an interpersonal perception test, than did the people in the study who read predominantly non-fiction, reports Oakley. One explanation could be that fiction is written in a way that encourages readers to identify with at least some of the characters, in this way suspending their own experiences to engage emotionally in those of others. Novels, stories, and dramas are wonderful entertainment, but, says Oakley, in helping us to negotiate the complexities of social interactions, they have far greater worth than that. Source: New Scientist, 28 June 2008.
Right: Narwhal (Monodon monoceros) with tusk (left upper canine). Photograph: Glenn Williams Right below: Illustrations of a male Arctic narwhal, with tusk (canine) growing from the left side of the upper jawbone (maxilla). Artwork: Kevin Hand
Watching whale-tusks grow T
he Arctic narwhal (Monodon monoceros) is a remarkable marine mammal. As the Latin prefix (‘mono’) indicates, the male grows a single tusk (the left upper canine), which can reach a length of 2 m. Researchers are currently attempting to estimate the rate of growth of these interesting tusks, as understanding their growth rate is relevant to the bigger question of how long the whales live. What we did was to examine a sequence of consecutively light and dark rings in a sectioned narwhal tusk, analysed microscopically at the Transvaal Museum, Pretoria, and chemically in the Archaeometry Laboratory at the University of Cape Town. We recognized alternating nitrogen isotope ratios, and found a remarkable correlation between them and the variation in the rings. Our conclusion is that these differences are associated with seasonal variability in the narwhal’s diet – they eat cod and shrimp in summer, and, by contrast, they feed on halibut in winter1. Analysing the rings furthers our understanding of the animal’s age. In addition, we have developed an equation expressing the relationship between tusk radius and length, as measured from its tusk tip. These data can be used in conjunction with other information for preliminary estimates of growth rates of tusks2, building on the pioneering study of Keith Hay (in 1984), who recognized that the tusks of young individuals grow at a faster rate than those of adults. In the context of recent work by Eva Garde and colleagues2, we conclude that growth rates for narwhal tusks are in the order of 100 mm per year for individuals between 6 and 7 years old. Amazingly, narwhals can live as long as a century2. Further analyses are in progress as we keep watching this whale. – Martin Nweeia (Harvard School of Dental Medicine) and Francis Thackeray (Transvaal Museum) ■ 1. M.T. Nweeia, J.F. Thackeray, F. Eichmiller, P. Richard, L-M. Leclerc, J. Lanham, and I. Newton, “Isotopic analysis of sectioned tusks of narwhal (Monodon monoceros) and tusk growth rates”, Annals of the Transvaal Museum (in press). 2. E. Garde, M.P. Heide-Jorgensen, S.H. Hansen, G. Nachman, & M.C. Forchhammer, “Age-specific growth and remarkable longevity in narwhals (Monodon monoceros) from west Greenland as estimated by aspartic acid racemisation”, Journal of Mammalogy, vol. 88 (2007), pp. 49–58.
Q Fact file More on the Arctic narwhal Climate change puts the Arctic narwhal at greater risk of extinction than even the polar bear, according to a study published in Ecological Applications in April 2008. Says co-author Ian Stirling (a specialist working for the Canadian government), “We’re talking about a whole ecosystem. We’re talking about several different species that use ice extensively and are very vulnerable.” Among the variables used to determine the ability to withstand a future warmer climate were population size, habitat uniqueness, diet diversity, and ability to cope with sea-ice changes. After the narwhal and the polar bear, the mammals most at risk were the hooded seal, bowhead whale, and walrus. Although there are still about 50 000–80 000 narwhals left (in contrast with some 20 000 polar bears), the problem is that they are specialist animals, evolved specifically to live in small cracks in parts of the Arctic where it is 99% heavy ice, explains lead author, Kristin Laidre (at the University of Washington). They dive about 1 830 m to feed on Greenland halibut and use restricted migration routes, which makes it hard for them to adapt to changing conditions. The melting ice changes their habitat, and also makes them increasingly vulnerable to predators such as killer whales. Reported by Seth Borenstein on www.foxnews.com, 25 April 2008. Arctic narwhals (‘unicorns of the sea’) have been relatively little studied. Found in Arctic waters, never far from ice, they are best known for the male’s characteristic single, straight, spiralled, ivory tusk. Researchers know it’s not used for hunting, but its exact role remains a mystery. Narwhals have two teeth in their upper jaw. After the first year of a male’s life, its left tooth grows outward to create the tusk, which projects from the upper jaw. The name ‘narwhal’ (from Old Norse) means ‘corpse whale’, perhaps because the animals often swim belly up, lying motionless for several minutes. They swim in groups (pods) of up to 20, sometimes linking up to travel together in larger numbers. They can grow up to 4.5 m in length (excluding tusk). Information sourced from the internet.
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South African PhD Project
Expanding the frontiers of knowledge www.nrf.ac.za
National Research Foundation
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Dia mond & ma mmography screening Tom Nam describes how the use of diamond can improve the way that X-ray doses for mammography screening are measured.
ancers1 are named after the part of the body where the abnormal cell growth begins. Breast cancers, for example, are cancer cells from the breast. According to the statistics, breast cancer is the second most common form of cancer in women, after non-melanoma skin cancer. Figures relating to the American population indicate that in 2004 (the most recent year for which data are available), some 186 700 women and 1 800 men were diagnosed with breast cancer, and some 41 000 women and 360 men died from it. With such high numbers of people affected has come raised awareness of the illness. The prospect of recovery from breast cancer is higher when the disease is detected early. Mammography is the most sensitive breast cancer detection method currently available. Mammography screening, therefore, is the intervention most commonly recommended for early diagnosis, and more and more healthy women are checked for breast cancer by this means. But mammography is an X-ray technique involving ionizing radiation, so it can itself induce breast cancer if the equipment does not give the right dose. Determining the exact radiation dose from mammography X-ray beams is therefore a high priority. Measuring the X-ray dose Carrying out mammography dosimetry (that is, measuring the dose) requires a measuring probe. At present, an ionization chamber is the most common one. When coupled with an associated electronic system called an electrometer, it is used to determine the radiation dose. The most widely used radiation-sensing medium of the ionization chamber is air, which is susceptible to atmospheric changes. So using the ionization chamber for radiation-dose measurements means having to correct for air density, temperature, pressure, and humidity – and this can introduce some level of uncertainty into the measurements. What’s needed, therefore, is a dosemeasuring instrument with a radiationsensing material that is not influenced by atmospheric conditions. Diamond sensors, unlike air ionization chambers, are unaffected
by them. So employing a diamond probe reduces the number of variables used to evaluate dose quantities, in this way also reducing possible sources of error or uncertainty in the measurement. Because diamond’s response to radiation is close to that of human tissue, its response in measuring an X-ray dose requires little or no correction to tissue dose. Furthermore, diamond is a solid, so it has high sensitivity. This implies that diamond samples with physical sizes much smaller in volume than the size of an air chamber could be used – which brings down the cost of probe construction. The right kind of diamond As with most materials, however, the electronic behaviour of diamond depends on the types and concentrations of defects or impurities present in its matrix. This eliminates the use of natural diamonds for our purpose, as we have no control over their composition. Using them requires laboriously sifting and sorting many crystals to locate those that are suitable for radiationdose measurements. Through systematic characterization (using such tools as Raman spectroscopy, UV absorption, thermo-luminescence, electron spin resonance, and current-voltage measurements3), our research has identified the types of defect/impurity that govern the behaviour of artificial diamonds. An understanding of the physics determining the interplay of such defects/impurities has allowed our research group to highlight parameters that are important for the routine manufacturing of diamond wafers and/or crystals for applications in mammography as well as other fields. Milestone A now patented radiation measuring probe, with synthetic diamond as the radiation sensor, has been constructed and systematically evaluated for use in mammography by our group. We have found it to have a high level of radiation sensitivity and to be able to provide accurate radiationdose measurements. This diamond probe is easily adaptable to existing commercial
1. Cancer is the term used for any type of malignant growth or tumour caused by abnormal and uncontrolled cell division. It can spread through the lymphatic system or blood stream to other parts of the body. 2. These statistics come from Centers for Disease Control and Prevention, of the US Department of Health and Human Services. 3. For more on Raman spectroscopy, see “Techniques for investigating solid materials” in Quest, vol. 2, no. 1 (2005), pp. 13–14. For explanations of thermo-luminescence and electron spin resonance, see box on page 5 in the current issue.
Top: Natural diamond crystals, whose variable composition makes them unsuitable for use in measuring the X-ray radiation dose in mammography. Middle: Tissue-equivalent diamond probe (diamond is close to human tissue in its response to X-rays), using manufactured diamond. Above: Experimental setup for radiation-dose measurements from a mammography X-ray unit.
electrometers, so it does not require the addition of specially designed interfacing systems for its operation. Once again, diamond is proving to be one of woman’s best friends. ■ Professor Nam, a physicist and electrical engineer, is in the DST-NRF Centre of Excellence in Strong Materials and in the School of Physics at the University of the Witwatersrand. He has investigated the unique properties of synthetic diamond for use in medicine since the 1980s. Contributors to the work described here are Emeritus Professor Rex Keddy (also a member of the same Centre of Excellence) and Dr Mary Boadu of the Ghana Atomic Energy Commission, whose doctoral work investigated the use of diamond for mammographic screening. For details, read M. Assiamah, T.L. Nam, and R.J. Keddy, “Radiation doses from low energy X-ray beams measured with synthetic diamond compared with calculated values obtained from the PENELOPE Monte Carlo code”, Applied Radiation and Isotopes, vol. 65 (2007), pp.952–958.; and visit http://web.wits.ac.za/Academic/Centres/ StrongMaterials/Diamond.
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Malachite sunbird (Nectarinia famosa) at Goegap Nature Reserve. Photograph: Tim Jackson
Sue Nicolson explores the attractions of sugary nectars for birds that pollinate some of South Africa’s most colourful plants.
The drinking habit s of sunbird s
Male white-bellied sunbird on Leonotis.
Photograph: Tim Jackson
any birds drink nectar and, while doing so, pollinate the plants they feed on. Best known are the African sunbirds, Australasian honeyeaters, and American hummingbirds – three unrelated families that for the most part live on different continents, but whose nectar-feeding habit has led to similarities in their behaviour, physiology, and ecology, as well as in the flowers they visit. The birds (often brightly coloured themselves) drink from conspicuous red or orange flowers – normally tubular ones in the case of hummingbirds, but brushlike flowers are also attractive to sunbirds and especially honeyeaters. To satisfy the high energy demands of bird pollinators, a plant has to produce big flowers, or inflorescences, with lots of nectar. In South Africa, the better known tubular bird flowers are species of Aloe, Erica, Leonotis (wild dagga), and Kniphofia (red-hot pokers), while brushlike flowers include Protea, Leucospermum (pincushions), and Greyia (the Natal bottlebrush). But sunbirds also feed willingly on the easily accessible nectar of introduced Australian brush flowers growing here, such as Callistemon (bottlebrushes) and Eucalyptus. Aside from the beauty of bird–flower associations, nectar-feeding birds are wonderful models for research into physiology, because their energy and water turnover are extreme and inseparable. Sugar-rich nectar is a relatively simple but very watery food. At the University of Pretoria we are studying details of nectar feeding in sunbirds, to find out more about what kind of food the nectar provides and how these birds cope with the huge amounts of water that pass through their small bodies. We are looking in particular at the whitebellied sunbird Cinnyris (Nectarinia) talatala, a savanna species that is familiar in Pretoria gardens. These small birds can be maintained in captivity on artificial nectar containing sucrose solution (for energy) and the health supplement Ensure™ (for protein, minerals, and vitamins). It is relatively easy for researchers to vary the diets and record the amounts consumed, to collect the fluid that the birds excrete, and to find out what nectars the birds prefer by giving them a choice of two or more diets simultaneously, each in a different feeder1. High energy needs Small size means high energy demands per gram of body mass and a fast lifestyle. This is especially true of hummingbirds, which hover at flowers, wings moving so rapidly that they become almost invisible. An 8-g white-bellied sunbird needs about 2.7 g of sugar each day – one third of its body mass. This energy can be obtained from nectar
1. In this sort of experiment we have to be careful about possible side bias – an individual bird might always want to drink from the righthand feeder – so feeders are switched at regular intervals.
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Dusky sunbird (Cinnyris fuscus) in hot weather, supplementing its liquid intake from a tap. Photograph: Tim Jackson
Top: Modified syringe containing sucrose solution and EnsureTM for feeding captive sunbirds. Photograph: Carolina Leseigneur Above: Compensatory feeding in white-bellied sunbirds. Values are means ± s.e. (standard error) for volume consumption in ml/day (open squares) and sucrose consumption in g/day (solid circles). Energy intake is constant over a wide range of sucrose concentrations, but decreases on concentrations below 0.25 M.
surprisingly quickly, and a sunbird spends only a few minutes out of every hour feeding. Its body mass changes continually, because of its frequent nectar meals and excretion, but increases gradually throughout the day to build up energy stores for the night, when the bird does not feed. The average concentration of nectars intended for avian pollinators is 20% on a weight/weight basis, which means that every 20 g of sugar comes with 80 g of water. But nectars vary in concentration – often because of evaporation from open flowers – and the more dilute the nectar, the greater the volumes the birds have to drink to maintain constant energy intake, in a phenomenon called compensatory feeding. Extreme water loads The more nectar the birds drink, the higher the rates of water turnover, which can be more like those of frogs or freshwater fish than of other birds. To obtain its daily energy requirement from a dilute Aloe nectar containing 10% sugar, a sunbird has to drink as much as 3.5 times its body mass. The equivalent for us humans would be a 70-kg person drinking 245 litres of Coca-Cola™ – which has a similar sugar concentration – in one day! All the surplus water must be eliminated, either by evaporation or by excretion, and excretion seems to be the main route. These are leaky little birds in chronic diuresis. How their bodies manage to pass so much water is the important physiological question. Their kidneys process extraordinary amounts of fluid, yet retain almost all the solutes. The result is huge volumes of remarkably dilute urine – in white-bellied sunbirds it’s as dilute as
Marico sunbird (Cinnyris mariquensis) on Erythrina humeana, photographed at Orpen Gate of Kruger Park. Erythrina is a pantropical genus, almost exclusively bird-pollinated, in which the inflorescence morphology and nectar properties differ in species pollinated by hummingbirds or passerine birds. Photograph: Tim Jackson
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Coloured nectar of Aloe castanea. Photograph: Massimo Nepi
Gurney’s sugarbird (Promerops gurneyi) foraging on Protea caffra, despite the high levels of nectar xylose (see box on opposite page). Photograph: Tim Jackson
For the definitive book on sunbirds, see R.A. Cheke and C.F. Mann, “Sunbirds” (London, Christopher Helm, 2001). For details about nectar chemistry, read S.W. Nicolson and R. Thornburg, “Nectar chemistry”, in S.W. Nicolson et al. (eds), Nectaries and Nectar (Springer, Dordrecht, 2007), pp.215–263. Some laboratory experiments on sugar and water intake, and bird sugar preferences, are described in S.W. Nicolson and P.A. Fleming, “Energy balance in the white-bellied sunbird, Nectarinia talatala: constraints on compensatory feeding and consumption of supplementary water”, Functional Ecology, vol. 17 (2003), pp.3–9; and P.A. Fleming et al., “Concentration and temperature effects on sugar intake and preferences in a sunbird and a hummingbird”, Functional Ecology, vol. 18 (2004), pp.223–232.
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tap water. In addition, sunbirds on dilute diets reduce the water load on their kidneys by shunting some of the water directly through the intestine, instead of absorbing it all in the way that hummingbirds do. This explains why sunbirds are better able than hummingbirds to cope with more dilute nectars. Winter brings further demands, as nectar-feeding birds have to warm cold food to body temperature – this is an energetically expensive business when the nectar is dilute. A sunbird consuming Aloe nectar on a chilly winter morning must warm large volumes to its body temperature of 40 °C (penguins eating cold fish in Antarctic waters have a similar problem). Although an overabundance of water is the norm for sunbirds, there are circumstances in which they need to supplement their intake by drinking – in very hot weather or if only concentrated food is available.
Which sugar tastes best? The three main sugars in nectar are sucrose and its component monosaccharides, glucose and fructose, which tend to be present in equal concentrations. Incomplete breakdown of sucrose is common, and results in a mixture of the three sugars in the nectar of a single flower. Sometimes nectar sugar composition has taxonomic value2; for example, all Aloe species sampled have hexose (glucose/fructose) nectars with only small amounts of sucrose, while all species of the closely related genus Gasteria have nectars that are almost pure sucrose. Specialized nectar feeders such as
hummingbirds and sunbirds go for nectars that are rich in sucrose, while many birds that feed occasionally on nectar prefer nectars rich in glucose and fructose. The distinctive genus Erythrina is a classic example, having nectars that are quite different in species pollinated by hummingbirds (in South America) from those pollinated by generalized passerine birds (in Africa and South America)3. This has led to speculation about what sugars different bird families may prefer. Our group, with colleagues in Australia and the USA, have recently examined the sugar preferences of sunbirds, hummingbirds, and honeyeaters, using sucrose and glucose/fructose mixtures of the same molar concentration4 and therefore the same energy content. None of these birds shows strong sugar preferences, but when nectar is dilute, they tend to prefer hexoses to sucrose. The general lack of sugar preference is because all three bird families possess high activity of the intestinal enzyme sucrase, which hydrolyses5 the sucrose. The preference for hexoses when nectar is very dilute may be because sucrose is difficult to hydrolyse under these conditions. It seems that the difference in sugar composition of passerine and hummingbird nectars may have more to do with plant phylogeny (evolutionary history) than with the birds’ sugar preferences after all. Certainly there is not much overlap (on the different continents) in the major plant families that are visited by passerines and hummingbirds. Other constituents Nitrogen from amino acids. Amino acids number among the other constituents of nectar that are important to bird consumers. They occur in some South African bird nectars – a few Aloe and Erythrina species – at high concentrations; higher than those reported for any nectars that are favoured by insects. While non-essential amino acids are the most abundant, some or all of the essential amino acids (that is, those that cannot be synthesized by the body and need be taken in as part of the diet) are also present. Our group has looked at the response of white-bellied sunbirds to amino acids common in nectar, and we’ve found that they reject artificial nectar solutions when the concentrations of amino acids are too high. The nectars of bird flowers are ‘energetically dilute’, however, and birds have to drink large volumes to meet their energy requirements, so the nitrogen intake from the amino acids in the nectar might nevertheless be a useful supplement to that obtained by eating insects and spiders (or even pollen, which gets knocked into the nectar). Note that sunbirds feed insects, not nectar, to their chicks. Salts. Sunbirds also need salts, which they get from insects as well as from nectar. Sodium and potassium ions are also available from nectar,
2. Having ‘taxonomic value’ in this context means that nectar sugar composition is a taxonomic indicator for different types of plants. 3. Passerines are birds belonging to the Passeriformes, a very large order of birds characterized by their habit of perching. It includes larks, finches, crows, thrushes, and starlings. (For a picture of a sunbird on Erythrina, see p. 29.) 4. Mole is the SI unit of ‘amount of substance’; a ‘molar’ solution contains one mole of solute per litre of solution. 5. Hydrolysis is defined as a chemical reaction in which a compound reacts with water to produce other compounds. (When a substance is hydrolysed, it undergoes or is subjected to hydrolysis.)
Q Fact file Bird nectars in flowers and are probably physiologically important because sunbird kidneys cannot recover all ions from the enormous volumes of urine they produce. Preference tests using normal strength artificial nectar show that sunbirds are not particularly sensitive to added salts, but they become more so when the nectar is very dilute and the problem of salt retention becomes more acute. By way of comparison, fizzy drinks that people enjoy are low in minerals, but the sports drink, Energade™, which is used for rehydration, contains carbohydrate (8%) and plenty of sodium, and fruit juices contain high potassium. Nectar can be toxic Secondary metabolites6, which defend plants against herbivores, can occur in nectar as an inevitable consequence of their production in leaves, stems, and roots. For a plant, there’s an interesting trade-off here between attracting pollinators and repelling herbivores. It has been claimed that secondary metabolites in nectar may be useful to keep pollinators moving, encouraging them to visit more plants, and discouraging unwanted pollinators. Certainly the taste of nectar is affected. This is a new area of research, and most investigations of the responses of pollinators have involved alkaloids well known to humans, such as caffeine and nicotine. Honeybees choose mildly caffeinated solutions in preference to those without caffeine, for instance (and bees like to drink from CocaCola™ cans). Both sunbirds and hummingbirds are repelled by nicotine in nectar. The responses of pollinators depend on the sugar concentration as well as the concentration of the secondary metabolite. And responses to toxic nectar in free-living birds depends on what else is flowering at the time. Soft drinks for birds Nectar is a rich and easily utilized food that comes in attractive packaging. The same is true of soft drinks, hugely popular with people around the world, and there are many similarities between the sugar concentrations and other ingredients of soft drinks and the dilute nectars that birds like best. These constituents include preservatives, present in nectar in the form of proteins that inhibit bacterial growth. Some nectars are even coloured, such as the reddish-brown nectars in some Aloe species. The big difference between sunbirds and humans, however, is that sunbirds drink sugar solutions all day without putting on weight, and they tolerate high blood glucose levels that would cause diabetes in humans! ■ Professor Nicolson is in the Department of Zoology and Entomology at the University of Pretoria. She has a special interest in the physiological aspects of pollination biology. 6. The term ‘metabolism’ refers to the sum total of the chemical processes that occur in living organisms, resulting, for example, in growth, production of energy, and elimination of waste material. A metabolite, in the broad sense, is a compound that takes part in or is formed by these chemical processes or reactions.
Why are many bird flowers red? Red flowers are reputed to be invisible to bees, but this is not true – bees often visit red flowers. Nectar-feeding birds have no innate preference for red, but they learn easily to associate reward and colour. Nectar is a patchy resource and birds need to move around to find it: red and green are known to artists as complementary colours, and red stands out against a green leafy background better than any other colour. Why are bird nectars dilute? Various hypotheses have been proposed to account for the relatively low sugar concentration of bird nectars compared to those consumed by insects. ■ Low viscosities enable more efficient extraction of nectar by bird tongues ■ Low concentrations discourage bees ■ Dilute nectars are necessary to meet the water requirements of birds ■ Nectar is protected from evaporation in tubular flowers ■ Dilute nectars may encourage birds to visit more flowers ■ Dilute hexose nectars have a higher total solute concentration, which draws additional water from the nectary. None of these explanations is entirely satisfactory, and perhaps a combination of factors is involved. Laboratory experiments show that both sunbirds and hummingbirds prefer more concentrated sugar solutions than their natural nectars. An unusual nectar sugar in Protea Protea nectar is unusual in containing a fourth major sugar, xylose (as does its sister genus, Faurea). However, xylose is absent from other South African and Australian genera of the Proteaceae. We have examined the responses of various birds – sunbirds, sugarbirds, and white-eyes – to nectar xylose, and they don’t like it. Nor do bees, even though Faurea species are major bee plants in South Africa, so the significance of high xylose concentrations for pollination is not at all clear. Lack of gut sucrase in some birds If nectar sucrose has not been broken down to glucose and fructose in the flower, this has to happen in the bird’s intestine. Glucose and fructose are then absorbed through the intestinal wall and enter the blood. However, intestinal sucrase, the enzyme that breaks down sucrose, is lacking in a large group of frugivorous birds belonging to the sturnid-muscicapid lineage (such as starlings and thrushes), and starlings – very sensibly – avoid sucrose in preference tests. Eating it can be fatal for them. This lack of intestinal sucrase was once thought to be common to all passerine birds, and to explain the dominance of hexose sugars in many of their nectars, but this is now disproved. Sunbirds have high sucrase activity in their intestines and can handle all nectar sugar combinations well. Occasional nectarivores The large golden inflorescences of Aloe marlothii, conspicuous on northern rocky hillsides during the dry winter months, are visited by few sunbirds but by a varied assortment of larger birds with shorter bills such as insectivores and frugivores. Unlike sunbirds, these are not specialized nectar feeders. Weavers, bulbuls, and mousebirds are common examples. For these thirsty birds, the nectar provides both water and energy, and supplements other dietary components such as seeds and insects. This category of occasional nectarivores is important in southern Africa. Above right: Blackheaded oriole (Oriolus larvatus) foraging on Aloe marlothii. Photograph: Tim Jackson Right: Inflorescence of Aloe marlothii. Photograph: Craig Symes
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Bavesh D. Kana and Digby F. Warner examine the factors leading to drugresistant tuberculosis – and the consequences for managing this devastating disease.
Right: Acid-fast staining of M. tuberculosis, visualized in purple, in infected tissue. This laborious method, developed by bacteriologist Franz Ziehl and pathologist Friedrich Neelsen in Germany in the late 1800s, is still used today to detect bacteria in the sputum of infected patients. Below: A researcher at the Molecular Mycobacteriology Research Unit (MMRU) performing a routine technique (assessing bacteria on solid media).
uberculosis (TB) is a leading cause of mortality in South Africa and, together with the human immunodeficiency virus (HIV), seriously burdens an already struggling national healthcare system. It’s estimated that about one-third of the world’s population is infected with Mycobacterium tuberculosis (MTB), the bacillus that causes the disease. In many infected individuals, MTB lies dormant with no external symptoms: it’s thought that only about 10% of all infections result in active disease. But developing countries suffer the highest incidence of TB, and, where HIV is endemic, coinfection dramatically raises the risk of TB. In an HIV-positive person, for example, an estimated 10% lifetime probability of developing active disease turns into a 10% annual risk. The lethal synergy between HIV and TB, therefore, poses the single greatest threat to public health in countries such as South Africa – recently compounded with the increasing emergence of mutant MTB strains resistant to anti-TB drugs. What causes drug resistance? What can be
done about it? These are questions that researchers are grappling with. TB can be cured In 1993, the World Health Organization (WHO) declared TB a “global emergency” and formulated the Stop TB strategy. At the heart of it was DOTS1 (for ‘directly observed therapy, short course’), a treatment plan based on a combination of several different types of antibiotics to be administered over an extended period of six months. By treating active, infectious disease, DOTS represents the best global efforts to combat TB: it works by interrupting the transmission of the causative agent, MTB. To make sure that patients comply with therapy, the ‘DOT’ component was defined by the WHO as “watching patients take their medication”. In other words, the system requires the supervised administration of combination therapy to patients presenting with ‘sputum positive’ TB (a diagnosis of active TB disease made on the basis of visible bacteria in a patient’s sputum). Clinicians, healthcare workers, and community-based support staff or volunteers are meant to observe TB
1. The standard DOTS regimen requires the administration of four anti-TB drugs for at least six months. The first two months (‘intensive phase’) comprises therapy with frontline drugs such as isoniazid, rifampicin, and pyrazinamide, supplemented with either ethambutol (not recommended for use in infants) or streptomycin if resistance seems likely. Next comes a four-month ‘continuation’ or ‘consolidation’ phase of therapy with isoniazid and one other frontline drug, normally rifampicin.
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Drug-resistant TB in South Africa
How drug-resistance mutations develop
Q Fact file TB facts and stats
Above: Spontaneous mutations in target or complementary genes can confer resistance to a single antibiotic. Once acquired, the resistance mutation is transferred from the parental cell to its offspring – that is, the resistance is amplified and then maintained (fixed) in the population because, in the presence of the antibiotic, it confers a growth (selective) advantage on those cells that possess it. Combining drugs reduces the pathogen population to the point where it is unable to re-initiate infection (in effect, it ‘sterilizes’ the infecting population).
patients taking drugs so as to empower them to strive for better health. For effective DOTS roll-out, however, this strategy needed the strengthening of primary healthcare systems in ‘highburden’ countries (that is, where a high proportion of people are affected). In 1994, DOTS became WHO policy, and was officially adopted by South Africa in 2001. In addition to ensuring individual compliance with the drug regimen, it was expected that political commitment to TB treatment, and regular evaluation of programme performance, would improve success. Where fully implemented by wellfunded national TB control programmes, DOTS has improved the outcomes of treatment and limited the development of drug resistance. But in many areas, adopting the DOTS programme has been slow, and coverage remains inconsistent. Further erosion has come from the HIV pandemic – and by patients’ failure to comply with treatment. Implementing the long regimen is challenging and fraught with complications, in particular by the need to continue the therapy rigorously, even after a patient starts feeling better. Together with inappropriate treatment regimens, then, and intermittent drug supply in resource-poor settings, failed
compliance has significantly helped drug resistance to evolve. Sadly, the global emergence of drug-resistant MTB strains is a threat to DOTS – and, by implication, to global control of TB. What defines MDR- and XDR-TB? Bacteria that can resist the effects of compounds designed to limit their growth (bacteriostatic compounds), or even to kill them (bacteriocidal), are termed ‘resistant’: put simply, resistant bacteria grow in the presence of the antibiotic. And resistance to a specific antibiotic renders that antibiotic ineffective (inappropriate) for treatment of the disease. Resistance to at least the two frontline TB drugs, isoniazid and rifampicin, constitutes multidrug-resistant TB (MDRTB). Extensively drug-resistant (XDR) TB is, in turn, defined by the WHO Global Task Force on XDR-TB as MDR-TB plus resistance to (i) any fluoroquinolone, and (ii) at least one of the three secondline injectable drugs – capreomycin, kanamycin, or amikacin. These definitions suggest that MDR and XDR-TB are not single strains of MTB: in theory, any MTB strain can acquire sequential resistance to isoniazid and rifampicin to become MDR and, similarly, any MDR strain can be converted to XDR through
■ A recent study at a Johannesburg hospital showed that 95% of patients presenting with HIV are co-infected with the TB bacillus*. ■ The World Health Organization (WHO) estimates that 44% of all TB cases in South Africa are associated with HIV co-infection – and that South Africa accounts for almost one-third (28%) of HIV-positive TB cases globally (www.who.int/globalatlas). ■ As of 17 March 2008, the WHO recorded a TB incidence of 628 per 100 000 population in South Africa, placing it among the top five highest incidence countries worldwide. The others in the top five are Lesotho, Namibia, Djibouti, and Swaziland (www.who.int/globalatlas). ■ Accurate numbers of MDR and XDR cases remain unknown owing to inadequate drug susceptibility testing, and poor reporting in many countries including South Africa. ■ According to current estimates, the cost of treating drug-susceptible TB is about R375 per patient; in contrast, approximately 130 times that amount (about R50 000) is required to cure an individual infected with an MDR-TB strain. ■ The 2008 South African National Tuberculosis Programme had a budget of US$352 million; of this amount, around 20% is devoted to DOTS implementation, and 70% is applied to the problems of MDR- and XDR-TB. ■ The WHO estimated that at least US$2.1 billion would be required to tackle the MDR and XDR problem in 2007–2008 (www.who.int/tb/challenges/xdr). * See M.A. John et al., “High tuberculosis and HIV coinfection rate, Johannesburg”, Emerging Infectious Diseases, vol. 13 (2007), pp. 795–796.
mutations conferring resistance to a fluoroquinolone and a secondline injectable drug. This fact has often been ignored in media reports erroneously implying that XDR-TB is a single, ‘plague-like’ organism that threatens to sweep across the globe. The potential for the MDR and XDR phenotypes2 to arise in any strain background, in any setting worldwide, has major implications for the correct application of the DOTS system, and demands vigilance in efforts to detect the emergence – and limit the spread – of these strains. It is of concern, therefore, that a WHO report released early in 2008 indicated that MDRTB rates were at their highest ever, accounting for half a million new cases each year – or approximately 5% of the almost nine million new TB cases. For the first time, this survey also included estimates of the global prevalence of XDR-TB: some 80 countries took part, and more than half reported cases of XDR-TB.
2. A phenotype is a term used for the physical constitution of an organism as determined by the interaction of its genetic constitution and the environment.
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Researching multiple drug resistance
* Research at the Molecular Mycobacteriology Research Unit (MMRU) is currently directed at identifying processes that contribute to drug resistance, and the effects of drug resistance on TB pathogenesis. ** This question is also being addressed in the MMRU – in particular, through the use of molecular genetic methods to construct specific drug-resistant mutants and to assess the ability of the resultant strains to grow under different environmental conditions.
The ability of bacterial pathogens such as MTB to infect people, survive, reproduce, and be transmitted to others, is encapsulated in the concept of ‘fitness’. Antibiotics target mechanisms or pathways that are essential for many of the processes contributing to fitness, including cell wall synthesis (for example, isoniazid and ethambutol), DNA replication (fluoroquinolones) and transcription (rifampicin), and protein synthesis (streptomycin). By implication, where resistance to antibacterial agents comes from mutations in the drug targets themselves, we can expect that essential pathways – and therefore fitness – are likely to be affected. That is, when a strain mutates to become drug-resistant, the mutation(s) normally undermines the ability of the resultant mutant to grow and survive during infection in the absence of the selective pressure of the antibiotic. In other words, that strain displays reduced fitness – the mutation to drug resistance seems to come with a ‘trade off’. The emergence of MDR and XDR strains resistant to multiple antibiotic agents raises fundamental scientific questions relating to the ability of the resistant strains to continue to grow, cause disease, and compete with other bacteria, after they have sustained sequential resistance-conferring mutations in essential pathways. These questions include the following. How does evolving resistance affect the overall biology (pathogenesis) of the TB bacillus*? Are fitness ‘costs’ the same for all drugs**? Are fitness costs cumulative (do multiple mutations affect fitness, and is there a limit to the number of resistance mutations that can be accommodated without irreversibly crippling fitness)? Can fitness costs be offset by other mutations? Does the strain’s genetic background influence the kinds of antibiotic resistance that can be tolerated – that is, are certain combinations of resistance-conferring mutations more readily accommodated in some strain backgrounds than others?
The Tugela Ferry tragedy In 2006, an outbreak of XDR-TB was reported at the Church of Scotland Hospital in the Tugela Ferry region of KwaZulu-Natal. Of 221 cases identified as MDR-TB, about a quarter were found to be carrying XDR-TB. All of these patients were co-infected with HIV. Tragically, 52 of the 53 XDR patients died, raising fears that this incident might signal the spread of an essentially untreatable, fully virulent strain of MTB across the country, and perhaps the world. This case hit the media globally, and thrust the problem of XDR-TB into public consciousness. Now we know that XDR strains are prevalent throughout South Africa, and more widely distributed around the world than initially thought. But inadequate drug susceptibility testing capabilities in many countries with a high TB burden (including South Africa) means that the true prevalence of XDR-TB worldwide remains unknown. In addition, key questions relating to the transmission and virulence of XDR strains in immune-competent communities remain unresolved and are the subject of ongoing research. In the case of the Tugela Ferry infections, all the XDR-TB patients were HIV positive: the association of XDR-TB with HIV was, therefore, biased. Subsequently, XDR-TB has been identified in immune-competent patients from many regions in many countries4. It would seem, therefore, that all infected patients are at risk of developing resistant organisms, irrespective of the strain with which they are infected. How antibiotic resistance develops Most often, resistance to antibiotics arises through spontaneous changes in an organism’s genetic content. These changes (or ‘mutations’) are the basis of evolution. Where a mutation occurs in a gene(s) that encodes a specific drug target(s) – or in an accessory gene(s) – it can result in drug resistance. Resistance is not limited to mutations, however, but can also arise through the acquisition of mobile genetic elements. Unlike most bacterial pathogens, all drug resistance in MTB results from mutations in those genes that encode specific drug targets, or in complementary genes encoding proteins
Above: A researcher at the MMRU culturing microorganisms. This is a standard technique in microbiology, used here in the study of drug-resistance mechanisms in mycobacteria and the evolution of MDR and XDR strains of TB.
34 Quest 4(3) 2008
that contribute to, or affect, drug action. For example, the frontline antiTB drug, rifampicin, interferes with transcription of RNA by binding to an enzyme called RNA polymerase, which is responsible for this function. Strains that are resistant to rifampicin possess mutations in one gene encoding a critical component of the RNA polymerase enzyme; it’s important that most of these mutations fall within a defined area of the gene that is able to tolerate these genetic changes. Resistance to rifampicin, therefore, provides an example of a resistance mutation in a target-encoding gene. In contrast, resistance to the other major frontline drug, isoniazid, depends on a mutation in a complementary gene involved in the drug’s action. But, while most drug-resistance mutations are associated with certain genes or regions, this is not true of all drug resistance. Instead, there are strains in which the resistance-conferring mutations cannot be identified, and remain undefined. Perhaps other resistance mechanisms operate in these strains (for example, modifications of drug uptake or efflux systems that prevent the intracellular accumulation of the antibiotic compounds). What causes resistance Key factors regularly cited to explain the development and spread of drugresistant TB include poor adherence by patients to the lengthy TB treatment regimen, the use of inappropriate antiTB drugs, and prolonged periods of infectiousness due to delays in drug susceptibility testing. What role do these factors play in the emergence and spread of drug-resistant strains in the human population? Changes or mutations can occur at any position on the MTB chromosome: those able to confer resistance – by interfering in some way with the drug’s action – are maintained (amplified) in the bacterial population because of their advantage in the presence of the drug (see figure on page 33). Statistically, the chance of a population of MTB bacteria sustaining a drug-resistance-conferring mutation is low – about 1 in 10 million (10–7). That is, a population of a billion (109) bacteria in the lungs of a person with TB could theoretically contain about 100 spontaneous drug-resistant
4. Local researchers, for example, identified an outbreak of drug-resistant TB in the Western Cape involving strains of MTB that belong to a new strain family, distinct from that which was identified in the Tugela Ferry region. This new strain seems to have evolved in a step-wise fashion, from a fully drug-susceptible ancestor, to give rise ultimately to strains resistant to up to as many as five TB drugs. For details, see T.C. Victor et al., “Spread of an emerging Mycobacterium tuberculosis drug-resistant strain in the Western Cape of South Africa”, International Journal of Tuberculosis and Lung Disease, vol. 11 (2007), pp. 195–201.
Drug-resistant TB in South Africa
mutants (10–7 x 109 = 102). To fight them, a combination – or cocktail – of different anti-TB drugs is administered together. The principle underlying such ‘combination therapy’ is that the probability of a single bacterium simultaneously carrying mutations that can confer resistance to two or more drugs is extremely low (much less than one in a trillion; 10–7 x 10–7 = 10–14). The emergence of MDR and XDR strains of MTB that carry multiple resistance-conferring mutations betrays failure to adhere to fundamental tenets of antibacterial therapy; each public-health factor mentioned above (poor compliance, inappropriate therapy, prolonged infectiousness, and insufficiently rapid detection of resistance strains) undermines the effectiveness of combination therapy. The severely compromised immune response of HIV-infected patients also alters progression of TB disease, which could affect drug resistance3.
Above: Drug resistance develops when the bacteria that cause TB are not exposed to the correct concentrations of drugs for the prescribed amount of time. If a patient presents to a clinic with active TB, and the infecting strain (represented as black spots) displays no pre-existing drug resistance, antibiotics will normally clear the bacteria and make the disease symptoms disappear after initial treatment (A). If the patient complies with the treatment, almost all the bacteria will eventually be killed and the symptoms of disease eradicated; the patient is cured. In many cases, however, not all the bacteria are killed and a small sub-population of them remains behind. These have the capacity to resume active replication and cause disease if the patient becomes immunecompromised through, for example, advancing age, diabetes, or HIV infection (B). Where the prescribed treatment is not followed for the full length of time, concentrations of antibiotics in the blood and lungs fall below the range needed to kill the bacteria. Bacteria exposed to this sub-optimal concentration of antibiotics can adapt, survive, and, ultimately, become drug-resistant. The first and most likely case is the evolution of single (mono) drug resistance (C, where red spots represent mono-resistant bacilli). These mono-resistant bacteria can multiply again, amplifying the resistant population and leading to disease requiring re-treatment (D). A patient’s non-compliance can cause resistance to a second drug to evolve (E), giving rise to multi-drug-resistant (MDR) strains (blue spots). Alternatively, MDR can evolve in a single step as a result of noncompliance during the initial round of treatment (F). Patients carrying MDR-TB can transmit this form of the disease to others (G). Many people can be infected with drug-resistant strains, which makes treatment difficult, even if newly infected patients comply with the treatment regimen. Further mismanagement of MDR-TB by the prescription of inappropriate or ineffective anti-TB drugs (particularly in the absence of effective drug susceptibility testing), or by non-compliance, can ultimately lead to the development of resistance to second-line antibiotics (H), and to extensively drug-resistant (XDR) TB.
TB only after they fail to respond to standard treatment. Furthermore, even where testing has taken place, several months can pass before the diagnosis is confirmed, resulting in dangerous delays in administering second-line drugs. During this period, the risk of transmitting MDR strains to others is high and, where patients are co-infected with HIV, there is a strong likelihood of death. New tests, however, will enable the rapid determination of a drug-resistance profile, which should result in the prescription of appropriate drugs, rather than drugs that will be ineffective and, more worryingly, amplify resistance. ▲ ▲
Fighting resistance Given the relatively few anti-TB drugs available, prudent use of the drugs that we know is crucial and the subject of active research. Considerable efforts are also being directed towards the development of novel antibacterial agents to inhibit bacterial components not previously considered for antibiotic targeting. Whereas most current antibiotics target processes that are essential for the growth of bacteria, new strategies have been proposed to target alternative processes – those required for the bacterium to cause disease, but not essential for its survival. Such targets include factors required for virulence, as well as the very processes implicated in the generation of mutations. In this way, the usefulness of antibiotics can be prolonged. Perhaps the greatest single problem for TB control in high-burden countries is the time it takes to reach a positive diagnosis of drug-resistant TB – compounded by HIV co-infection, which can mask factors that routine TB diagnosis takes into account. Molecular diagnostic tests now available can distinguish certain drug-resistant strains by assessing the target gene mutations most commonly associated with drug resistance. Most TB patients in developing countries, however, are tested for drug-resistant
How drug-resistant TB can evolve
3. The effect of HIV infection on the emergence of drug resistance is unknown. On the one hand, the bacterial numbers are elevated, therefore increasing the likelihood of resistance. This could be countered by a compromised immune system, which might affect the emergence of resistance. Additional questions include the diffusion of drugs (TB in HIV patients affects numerous areas of the body), as well as the possibility that less ‘fit’ resistant mutants could survive in an immunecompromised host (but would be eliminated in immune-competent hosts).
Above: Rifampicin-resistant isolates of a non-pathogenic mycobacterium, M. smegmatis. This strain is used routinely as a surrogate in drug-resistance studies of M. tuberculosis in analyses that provide insight into the mutation rates of these organisms.
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For more on TB, visit these websites: World Health Organization (www. who.int/tb/en); FIND Diagnostics (www.finddiagnostics.org); The Global Alliance for TB Drug Development (www.tballiance.org); the Molecular Mycobacteriology Research Unit (http://web.wits.ac.za/ academic/health/Research/MMRU). For related research, consult D.I. Andersson, “The biological cost of mutational antibiotic resistance: any practical conclusions?” Current Opinion in Microbiology, vol. 9 (2006), pp.461–465; E.C. Böttger and B. Springer, “Tuberculosis: drug resistance, fitness, and strategies for global control”, European Journal of Pediatrics, vol. 167 (2008), pp.141–148; N.R. Gandhi et al., “Extensively drug-resistant tuberculosis as a cause of death in patients co-infected with tuberculosis and HIV in a rural area of South Africa”, Lancet, vol. 368 (2006), pp.1575–1580; M.J. Selgelid et al., “Ethical challenges in TB control in the era of XDR-TB”, The International Journal of Tuberculosis and Lung Disease, vol. 12 (2008), pp.231–235; J.A. Singh et al., “XDR-TB in South Africa: no time for denial or complacency”, PLoS Medicine, vol. 4 (2007), e50. ▲
On 30 June, 2008, the WHO announced the development of a rapid molecular diagnostic test for drug-resistant TB that will be used in developing countries over the next four years. It will ensure that patients with MDR are diagnosed within two days of sample collection (in contrast to the current 2–3-month period), which should significantly improve the outcomes of treatment.
As WHO Director-General Margaret Chan acknowledged, this initiative was enabled by results from a largescale pilot study conducted by the Foundation for Innovative New Diagnostics (FIND) in collaboration with South Africa’s Medical Research Council and National Health Laboratory Service. Their data confirmed the reliability and feasibility of the new molecular assays under routine laboratory testing conditions. Ethical, social, and legal issues Apart from AIDS, TB claims more lives than any other disease resulting from an infectious agent. Moreover, AIDS and TB are both associated primarily with disempowered people and those living in poverty. In addition to the profound challenges for public health, therefore, the number and status of people affected by TB and drugresistant TB raises important social, ethical, and legal concerns. Public attention has been drawn to issues such as the involuntary
confinement of MDR and XDR-TB patients, the obligation of infected individuals to avoid infecting others, the duty of healthcare professionals to notify regulatory agencies, and the distribution of economic and healthcare resources. Underlying each of these is the need to balance public health concerns with the rights of the individual – a concept most poignantly highlighted by well-publicized attempts of MDR-TB and XDR-TB patients to escape quarantine facilities. Managing such concerns with sensitivity will play a central part in future efforts to control this devastating disease. ■ Both authors are members of the DST-NRF Centre of Excellence for Biomedical TB Research, and based at the MRC/NHLS/WITS Molecular Mycobacteriology Research Unit. Dr Kana is a Senior Researcher in the MMRU and has studied mycobacterial genetics and bacterial dormancy for the past nine years. Dr Warner is a Medical Scientist in the MMRU and has worked in the field of mycobacterial genetics and drug mutation mechanisms for the past eight years.
News Q The case for early antiretroviral therapy for HIV/AIDS Currently, the approach to treating HIV in Africa is defensive, and focuses on the need to keep sick people alive for as long as possible. The World Health Organization recommends ‘universal access’ to antiretroviral therapy (ART), starting treatment when HIV-infected people’s CD4 count drops to around or below 200 cells/µl. With large numbers of people at imminent risk of dying from AIDS-related illness, this recommendation makes sense as an emergency measure. But there are problems. ■ By the time the CD4 count drops to these low levels, patients may be extremely ill; many will have contracted TB, which needs to be treated before they start ART. ■ In some patients, the CD4 count never fully recovers and may even remain lower than 200/µl. ■ Even after three years on ART, the probability of developing TB is markedly higher than in HIV-negative people. ■ Prolonged HIV infection appears to lead to irreversible damage to the immune system. These arguments encourage the idea of starting ART much earlier than is currently the practice in Africa, and an early start could also help the general population of people at risk of HIV infection. ■ ART brings a massive decline in the patient’s viral load – in most cases, the virus has become undetectable within a year of starting treatment. ■ People with such low viral loads have a reduced risk of infecting others. ■ The proportion of HIV-infected people in ART is greater among patients older than 40 years of age than among those under 30. This bias is a natural consequence of delaying the start of ART. It means that the most sexually active patients (that is, those most likely to infect a partner with HIV) are the least likely to be in ART. Starting HIV treatment much earlier would disrupt HIV transmission. ■ Diagnosing TB in HIV-positive people is not always easy, and HIV-infected TB patients can be an important undetected source of new TB infections. If so, early intervention against HIV (which would massively reduce the probability of TB infection among those who are HIV-positive) would also help to reduce the onward transmission of TB.
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There are arguments against starting ART early, however. ■ Its unpleasant side-effects – hence the argument that ART should begin only when a patient shows appropriate symptoms or when CD4 counts drop to ‘dangerously low’ levels. (On the other hand, side-effects diminish as drugs improve; and delaying treatment leads, in most cases, to at least one bout of TB and possibly other AIDS-related infections, all of which are lifethreatening.) ■ The costs of initiating ART early – these may be unacceptable to local governments and maybe even to donors. But if starting somebody on ART at the age of 30 adds a further 40 years of life, starting treatment five years earlier adds only 45/40 = about 12% to the cost. If earlier intervention significantly reduces transmission, the reduced number of new cases could result in a net saving in expenditure on ART. Mathematical models are urgently needed for this situation. ■ Possible non-compliance and increased probability of resistance – caused by earlier initiation of ART, to a much larger pool of people, most of whom do not feel ill at the onset of treatment. This problem is undeniable, but decreased transmission rates resulting from early treatment could eventually reduce the number of people on treatment*. To succeed, any plan to treat people more often, and to start ART much earlier, would need solid support from the affected people and their community leaders, as well as from the medical and political leadership at provincial and national levels. Furthermore, while such an intervention could dramatically reduce transmission, it should be supported by simultaneous efforts to reduce HIV incidence through behavioural changes and interventions such as the safe medical circumcision of males. We need to be far more ambitious about ways to stop the epidemic, rather than limit our thinking merely to ways of managing it. – Brian Williams (Chair of the Board of Trustees, SACEMA [DST-NRF Centre of Excellence in Epidemiological Modelling and Analysis], Stellenbosch) and John Hargrove (Director of SACEMA). * Testing people would be part of the task of getting rid of HIV altogether. The case reproduction number R0 is about 7 or 8 in countries with a mainly heterosexual epidemic, such as South Africa, and the life expectancy for HIV-positive people who do not receive ART is about ten years. Annual testing, therefore, should reduce R0 to below 1 and lead to the eventual elimination of HIV.
Q Your Q uest ions answered
Facing life on earth? QUESTIONS: Life on planet Earth – and the meaning of ‘capacitance’? When will the Sun stop producing the light and heat to keep the Earth habitable? What is ‘capacitance’? – Joseph Matuba, Matseripe Secondary School ANSWERS The Sun will continue to get bigger until its heat and radiation engulfs Earth in about 3–5 billion years, wiping out all life long before the planet burns out. Professor Maarten de Wit, AEON and Department of Geological Sciences, University of Cape Town As the Sun ‘burns’ its hydrogen fuel into helium (via nuclear fusion), the gradual accumulation of helium at the centre of the Sun makes the remaining hydrogen burn faster and hotter. That’s why the Sun is 25% hotter and more luminous today than at its birth 4.5 billion years ago. This will come to a head about 6 billion years from now, when the Sun becomes a red giant, and the inner planets will either be engulfed (Mercury and Venus, definitely) or burnt to a cinder (Earth and Mars). After that the tiny, helium-rich remnant of the Sun will settle down to become a white dwarf (with about half the mass of the current Sun, but occupying a volume only the same as our Earth!), gradually radiating its energy over the next few hundred million years and eventually becoming a black dwarf (but NOT a black hole). Professor Phil Charles, SAAO, Cape Town Capacitance is “the property of a conductor or system of conductors that describes its ability to store electric charge”. The capacitance (C ) is given by Q/V, where Q is stored charge on one conductor and V the potential difference between two conductors (or between a single conductor and Earth). It is measured in farads. Capacitance is more commonly applied to systems of conductors (or semiconductors) separated by insulators. Source: Oxford Dictionary of Science (Oxford University Press, 2005).
QUESTION: How can we help to reduce greenhouse gases? “The search for the missing carbon sink” (Quest, vol. 3, no. 4) says that
carbon dioxide contributes nearly 60% to the greenhouse gas effect created by people. Would you recommend a need worldwide to stop putting carbon dioxide into sparkling cool drinks? – Clive Wilcocks, Edenvale ANSWER The carbon dioxide ‘fizz’ in sparkling drinks represents too small a fraction of carbon being combusted on a global scale for this strategy to make a real difference. What would help is for people to reduce their burning of fossil fuels, including gas, oil, and coal – and, at a domestic level, to use energy more efficiently. A good incentive is to consider the cost of energy, and find ways to save money by, for instance, using solar-powered water geysers, and installing automatic controls to switch geysers off when hot water isn’t needed. To help to reduce greenhouse gases, you don’t have to do without – you just need to take care not to waste energy that isn’t being used to anyone’s benefit! Professor Harold Annegarn, Faculty of Science, University of Johannesburg QUESTION: How best to boil water in a pot? If you put a pot of water on to boil and want it to boil efficiently, should you take the lid off or leave it on? With the lid on, pressure can build up and boiling could take longer – but others argue that the lid should stay on for faster boiling. Who’s right? – Sue Maclaren, Harare ANSWER Pressure builds up only if the lid is screwed on (as in a pressure cooker). A normal lid placed on a pot will not allow pressure to build up inside. Consequently, the water boils much faster if you keep the lid on. That's because, with the lid off, the hot water heats the air immediately above it; this hot air rises by convection and escapes from the pot. It’s a very efficient process! Hold your hand (carefully) above an open pot of water that is heating up, and you will appreciate how strong these air currents can be. With the lid on, the heat is trapped inside the pot and the water boils faster. Professor Phil Charles, SAAO, Cape Town
Letter to Innovate and educate
n our most recent scanning of the South African science and innovation environment, the National Advisory Council on Innovation (NACI) found information that may be of interest to your readers on South Africa’s human development, income distribution, and performance in mathematics. We noted that gross domestic product (GDP) at purchasing power parity (PPP) per capita – that is, the value of all final goods and services produced within a nation in a given year divided by the average (or mid-year) population for the same year – has grown, from a level worth some US$6 500 in 2000 to almost US$10 000 in 2007. It has not been shared equally by all citizens, however, as the Gini coefficient (a formula designed to measure the level of income inequality) remained high. This is confirmed by the fact that almost half of our population survive on less than R462 per month. It is generally agreed that, to solve societal problems and progress towards the Millennium Development Goals, the key is human development, of which education is an important component. It seems encouraging that 75% of our adult population can read and write, but we desperately need more matriculants – and more who will continue studying and acquiring skills after leaving school. The government, through the Accelerated and Shared Growth Initiative for South Africa (ASGISA) and the Joint Initiative on Priority Skills Acquisition (JIPSA), has identified a serious shortage of engineers, technicians, and artisans to develop and maintain the country’s infrastructure, such as electricity, water, roads, and housing. But only 7% of the total number of matriculants who pass Grade 12 every year pass mathematics at Higher Grade as a subject. Students interested in these careers are in high demand, so we hope that more learners will take up the challenge, and in doing so contribute to the economy and to society. Dr Hermi Boraine, Senior Specialist: Science, Technology and Innovation Measurement, NACI Secretariat, Pretoria
For more information from NACI, visit www.naci.org.za
Address your letters and questions about science to the Editor, and fax them to (021) 789 2331 or e-mail them to firstname.lastname@example.org. (Keep letters and questions as short as possible, and include your name and contact details. We reserve the right to edit for length and clarity.)
Quest 4(3) 2008 37
Careers in S&T Q
Why mat hs count s Mathematics opens the doors to careers of every kind – especially in science, technology, engineering, and finance. Maths and measurements apply in many ways for different kinds of work. All you have to do is master what you need for your career of choice!
Getting back to basics Careers counsellor and educationist Kobus Maree examines why many young South Africans have problems with mathematics – and why tackling underachievement is the first step to success in the workplace. Scope of the problem Far too few black learners enrol for study in fields related to the natural sciences and technology, and most black students still lack equal opportunities to enter these areas. It has been claimed that, at the end of 2002, only between 1 000 and 2 500 black students in Grade 12 (not even 1% of South Africa’s total for that year) had passed matric with a C+ or higher grade in mathematics or physical science; Grade 12 results for 2006 and 2007 confirm that the situation has not changed significantly since then. Dramatic improvement is unlikely in the next few years, as indicated by the results of the Third International Mathematics and Science Study – Repeat (TIMSS-R)*, which in 1998 assessed progress since the previous TIMSS study of 1995. It revealed that South African mathematics learners achieved significantly poorer marks than their peers in all the other 37 participating countries. This result should be read together with those of the first systematic evaluation of learners’ skills in English, mathematics, and the natural sciences including biology in 2001, during which Grade 3 learners achieved a national average mark of just 30% in mathematics**. In the follow-up study, Grade 6 learners in 2004 (Grade 3 in 2001) averaged only 27%. Furthermore, it was established in 2007*** that a sizeable proportion of learners across various language groups were not functionally literate/numerate – amongst Afrikaans mother-tongue speakers the proportion was 1%; amongst English speakers the proportion was 4%; amongst African-language speakers it was 34%. S.J. Howie, Mathematics and Science Performance in Grade 8 in South Africa: 1998/1999 (Human Sciences Research Council, Pretoria, 2001). ** Department of Education, Draft Education for All Status Report 2002: South Africa, incorporating country plans for 2002 to 2015 (Department of Education, Pretoria, 2002). *** Hough & Horne Consultants (2007), “A comparative study: The language proficiency (English) and numerical skills of elite matriculants and presumptions and questions about affirmative action and ensuing actions.” (Website accessed 10 October 2007: email@example.com) *
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espite the transformation of education in South Africa, failure rates in mathematics at school and university remain unacceptably high, and the number of learners who leave Grade 12 with a passmark in both mathematics and physical science is unacceptably low. The problem is worst among black1 learners, especially in rural areas and townships. The gap between white and black students in terms of the quality of education and training they are offered, and their levels of achievement, is cause for grave concern. This is a serious problem, as Grade 12 marks still, for the most part, determine a learner’s acceptance into higher education institutions to study for careers in fields where the country is short of qualified people and, therefore, where jobs are available – in engineering, accountancy, and clinical technology, for example. How can the gap best be addressed? What can career counsellors offer? And what can teachers and parents do to help learners to overcome the hurdles? Underachievement in mathematics Many hypotheses have been proposed to explain why so many learners in South Africa underachieve in mathematics. Possible factors include the following2: ■ poor socio-economic background (often going hand in hand with
poor incentives for learners to study at home) ■ lack of appropriate teacher and learner support materials ■ lack of communication between schools and communities, in the sense that parents of underperforming learners are often insufficiently involved in schoolrelated matters, take no part in activities organized by the school, and do not engage in discussions with teachers about matters relating to their children ■ schools that are financially underresourced and that provide inadequate learning environments ■ poor-quality teachers and teaching (including many teachers’ poor command of English as the language of teaching and learning, inadequate subject knowledge, and lack of motivation) ■ language of teaching and training often not the learners’ mother tongue ■ inadequate study orientation on the part of learners (that is, where learners have a poor attitude to study, inadequate study habits, and insufficient problem-solving, criticalthinking, and decision-making skills). Research over the past few years shows that each of these factors individually and collectively, to a lesser or greater extent, contributes to
1. The terms ‘black’, ‘coloured’, and ‘Indian’ are used here to highlight inequities in the South African population that need to be rectified. 2. See J.G. Maree and J.M. Molepo, “Problem-centered approach to mathematics in grade 9 and 11 learners in the Limpopo Province of South Africa”, Psychological Reports (2005), pp. 732–736.
Ways to achieve in mathematics
Above: Maths tutorials, with male and female students on a par.
the problem. Underachievement in mathematics in South Africa is a national disaster. Maths is by far a learner’s most important optional subject for fields where the country needs people with the skills that underpin economic growth – such as the built environment (for example, engineering and architecture), economic sciences, and medicine (including dentistry). Achieving in mathematics constitutes vital survival equipment – for individual learners, as well as for any developing country.
that “Career guidance in whatever form … has a positive effect on intention to enter [higher education] …. The Department of Education should increase its support for career counselling initiatives in schools – particularly where learners are not in a position, or feel themselves unable, to discuss their future plans with parents or guardians …. This would involve … establishing the service in schools which have no such tradition.”4 Moreover, there is a dearth of appropriate assessment instruments for career counselling in a diverse South Africa. And where psychometric tests are used, they are too often used alone, instead of in a holistic and dynamic way that takes into account and draws on the learner’s personal traits and context. Some of the shortcomings of career counselling strategies that rely mainly on the results of psychometric tests are that: ■ counsellors who implement current career counselling models rely mainly on the results of profiles of psychometric tests ■ few psychometric tests are specifically designed for South Africa, and most North American and European tests currently used in the country are not as valid and reliable as required for its multiplicity of cultures ■ the value of test results is often exaggerated, with the career counsellor viewed as an expert
* According to Minister of Education, Naledi Pandor, “Facts and knowledge are important and learners need support from competent and knowledgeable learners. We need to devise interventions that restore the confidence of teachers.” See N. Pandor, “Dispelling myths about OBE”, available at http://edulibpretoria.wordpress.com/. Accessed 12 July 2008.
Appropriate career counselling Learners who know what they could and should be working for – not only in mathematics (as a short-term aim), but also in life (as a longer-term aim) – are most likely to succeed in work and life in general. Appropriate career counselling for all South African learners is becoming increasingly important – particularly in schools in previously (and currently) disadvantaged regions, where such facilities are still virtually nonexistent. Too many learners, even those who have passed Grade 12, lack vital life-skills, basic business sense, and workplace etiquette. Despite sustained policy efforts, the country’s occupational landscape is riddled with gross imbalances and rife unemployment (by some estimates it’s as high as 46%)3. There is evidence, as reported by education researcher Michael Cosser,
Photograph: Éva Plagányi-Lloyd
My 25 years of research indicate clearly that ■ most children are capable of passing mathematics at the level they need for admission to their study field of choice; although not everyone can obtain an A for Grade 12 mathematics, that may not be necessary for entry or success in a particular career ■ low IQ scores, or low scores for mathematical aptitude, do not necessarily predict failure; high IQ scores, or high scores for mathematical aptitude, do not guarantee success ■ personal traits are crucial, and ultimately coresponsible for success or failure: the following are particularly worth developing: the will to do well – in mathematics (or in any field!); perseverance; selfdiscipline; resoluteness; conscientiousness and hard work; determination; time and stress management; and emotional stability ■ learners and students have to be helped (by career counsellors, teachers, parents, guardians, and others) to take responsibility for their own actions ■ to achieve in mathematics, learners must acquire the limited, technical language of this field (and to ‘speak’ this language regularly!) – if a problem looks difficult, it helps to start by looking for a simple form of it and working from there ■ cooperative learning is important – learners should work in groups and learn by doing mathematics actively, listening to others, and explaining mathematics to others (use the ‘buddy’ system: study with a friend or two with whom you get along well and who also want to succeed in maths) ■ mastery comes from learning mathematics actively (work sums out; learn aloud; test yourself in writing and orally; every day, do your homework and revise the day’s class-notes again) ■ it helps to write at least two complete first and second mathematics examination papers under simulated examination conditions (see if you can finish within the time allowed). Consensus around Outcomes Based Education (OBE) is growing that ■ not everything needs to be discovered or learned in a group context ■ content is important: OBE does not mean that learners don’t have to learn certain basic, yet crucial information in mathematics by heart*.
3. Statistics obtained from educationist Sharanjeet Shan in 2003 indicated the skewing of South Africa’s career patterns as a result of the apartheid past and woefully inadequate career counselling received by black learners. South Africa’s population is about 46 million, of whom some 38 million are black, 4 million are white, 4 million are coloured, and 1 million are Indian. Yet black people accounted for just 337 out of a total of 21 422 accountants; 347 out of a total of 14 687 engineers; 3 out of a total of 4 024 dentists; and 12 out of a total of 497 actuaries. There seems to be no evidence that this unacceptable situation has changed significantly since 2003, yet, to this day, career counselling in South Africa is available primarily to people able to afford this expensive service. 4. M. Cosser, Factors Affecting Student Choice Behaviour in the Course of Secondary Education with Particular Reference to Entry into Higher Education. Research Report (Human Sciences Research Council, Pretoria, 2002), p. 93.
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Careers in S&T Q
whose recommendations should be accepted unconditionally and the learner excluded from the decisionmaking process ■ the client learner may be inclined to avoid the responsibility of making his/her own career choices, and to avoid self-exploration and -development ■ English is the main language of learning and teaching (as well as of testing), even where a learner may not be well versed in English. There is a clear need for multiple and flexible approaches to datacollecting that facilitates career counselling, and for a combination of approaches, both objective and subjective. This is because objective results (obtained by administering quantitative ‘tests’) as well as subjective results (obtained from evaluations based on individual narratives) are necessary for wellinformed or appropriate career decision-making. Career counselling, therefore, needs to help individual learners to find out for themselves what gives personal meaning, to interpret their own interests, to decide their own potential and career values, and to design career plans by drawing on the life themes that they as individuals have established and identified.
Improving school maths On 13 March 2008, the US National Mathematics Advisory Panel reported the “mediocre” maths performance of American students compared with other nations, and recommended a schools focus on key skills that prepare students for learning algebra*. Algebra coursework in the USA begins in late middle school – as does a fall-off in maths achievement. But, says the report, “students who complete Algebra II are more than twice as likely to graduate from college compared to students with less mathematical preparation.” Parents should teach even young children about numbers and measurements, it adds, and suggests that pre-kindergarten-to-eighth-grade math curricula focus on skills such as handling whole numbers and fractions and certain aspects of geometry and measurement. It offers each grade specific goals – for instance, proficiency in adding and subtracting whole numbers by the end of third grade, and mastery of multiplication and division of fractions and decimals by the end of sixth grade. Preparation for algebra, says the report, needs simultaneous development of “conceptual understanding, computational fluency and problem-solving skills”. It recommends the practice, used by most top-performing nations, of allowing enough time to study each topic in the curriculum until it is learnt sufficiently well for it not to have to be revisited later. For US students, mastering fractions is the greatest obstacle – ‘fractions’ needs to be the new catchword for maths teachers today. The panel analysed some 16 000 research publications, plus testimony and comments from hundreds of organizations and individuals, for information about how children learn. They found it important for students to master basic maths facts so well as to make recall automatic, stored in the long-term memory, leaving room in their working memory to tackle new processes: “For all content areas, practice allows students to achieve automaticity of basic skills – the fast, accurate and effortless processing of content information – which frees up working memory for more complex … problem solving”. As cognitive science has shown, said panel chair Larry R. Faulkner, “kids have to know the facts.” They also have to work. The “talent-driven approach to math, that either you can do it or you can’t, like playing the violin” needs changing, added Faulkner. Students depending on native intelligence learnt less, the panel found, than those who believed that success depended on how hard they worked. As someone once calculated, genius is 1% inspiration and 99% perspiration – maybe that’s true for maths achievement too. * National Mathematics Advisory Panel, Foundations for Success: The final report of the National Mathematics Advisory Panel (US Department of Education, Washington, D.C., 2008). (Available at www.ed.gov/MathPanel.) Reported in The New York Times, 14 March 2008.
Strategies to consider Undeniably, low achievement in mathematics in South Africa needs to be addressed. Whether or not OBE will help significantly remains to be seen5. What can be said with some certainty, however, is that introducing OBE and other measures such as Dinaledi schools is no magic bullet. A combination of strategies is needed. Here are some suggestions: ■ improvements to the way in which mathematics is taught and learned ■ renewed emphasis on assessing learners in meaningful and sensible ways – of using the assessments to help individuals to clarify for themselves what to strive for, and to build confidence in their ability to succeed ■ the (immediate) introduction of a year of compulsory community service for all graduating teachers and educational psychologists, to ensure that they teach and practise in deep rural and township schools
– with appropriate incentives (financial and otherwise) to make the experience attractive, inviting, and safe. This would help to alleviate shortages of expertise where needs are greatest, and could potentially help to develop relationships across the diversity divide, thus promoting understanding of the needs of disadvantaged communities. It’s time to reconsider the meaning of ‘career counselling’, to investigate the merits of a combined qualitative– quantitative approach, to instil hope and vision in learners as they plan their future careers (and, indeed, lives), and to provide them with the motivation they so badly need to go out and achieve. There is no quick fix, and no quick solution – but the challenges can be addressed productively if the will is there to do so, in teachers, in parents and guardians, and in the learners themselves. ■ Professor J.G. Maree is in the Faculty of Education at the University of Pretoria, and editor of Perspectives in Education and the South African Journal of Psychology. A triple doctorate, he works in career counselling; his research focuses on optimizing the achievement of learners and providing costeffective career facilitation to all persons. For more information, consult the following: C. Loyiso et al., “Study (Jyugyo Kenkyu), from Japan to South Africa: a science and mathematics intervention program for secondary school teachers”, in B. Atweh et al. (eds), Globalisation and Internationalisation in Mathematics and Science Education (New York, Erlbaum, 2007); J.G. Maree et al., “Predicting success among first-year engineering students at the Rand Afrikaans University”, Psychological Reports, vol. 93 (2003), pp.399–409; J.G. Maree, Unravelling Mathematics (Lapa Publishers, 2005); J.G. Maree et al., “Predictors of learner performance in mathematics and science according to a large-scale study in Mpumalanga”, South African Journal of Education, vol. 26 (2006), no. 3, pp.229–252; Nelson Mandela Foundation, Emerging voices. A report on Education in South African Rural Communities (Research report by the HSRC) (Nelson Mandela Foundation, Houghton, 2005); C. Simkins et al., Doubling for growth. Addressing the maths and science in South Africa’s schools (Centre for Development and Enterprise, Parktown, 2007); J.G. Maree et al., “Facilitating postmodern career counselling in the Limpopo Province of South Africa: A rocky ride to hope”, Australian Journal of Career Counselling, vol. 16 (2007), no. 3, pp. 62–70; T.S. Steyn et al., “Study orientation in mathematics and thinking preferences of freshmen engineering and science students’, Perspectives in Education, vol. 21 (2003), pp.47–57.
5. The success of the OBE system, introduced in 1998, will be assessed for the first time at the end of 2008.
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Girls doing science (maths is the key) Girls do just as well at maths as boys do, says the latest research, provided the conditions are right – and it opens up the world of science to anyone who wants to enter. Conditioning
Girls and boys on a par If you think boys are inherently better at maths than girls, you need a thinking adjustment! Mathematics is not only a fundamental science
1. D. Visser, “Mathematics – the critical occupational filter for women”, South African Journal of Science, vol. 85 (1989), pp. 212–214. 2. J.S. Hyde and M.C. Linn, “Gender similarities in mathematics and science”, Science, vol. 314 (2006), pp. 599–600. 3. I. Dar-Nimrod and S.J. Heine, “Exposure to scientific theories affects women’s math performance”, Science, vol. 314 (2006), p. 435.
Photographs: Courtesy of the Department of Science and Technology
Above: Measuring different things in different ways, and making sense of the results, is at the very heart of science.
The only notable gender differences emerging from the broader study were those related to activity level and aggression, where scores for males were found to be significantly higher, and where the magnitude of the difference between the genders greatly exceeded any other, including complex problem-solving ability. The main conclusion was that, across nearly all the tests, there was far more evidence of ‘gender similarities’ than of gender differences; within each group there was a spread of abilities, and these spreads tended largely to overlap. A study by Ilan Dar-Nimrod and Steven Heine3 showed that women’s ▲ ▲
There’s no reason for girls to fare worse than boys in mathematics – a subject that, in South Africa’s past, was commonly viewed as the domain of (white) men. So when girls chose to prove themselves in other fields, conditioning could have been a reason. In a 1989 South African study, psychologist Deléne Visser1 concluded that ■ parents had higher expectations of their sons’ mathematical achievement than of their daughters’ ■ maths was still regarded as a male activity ■ parents’ expectations and encouragement were an important predictor of achievement in mathematics, especially in the case of Grade 9 girls on the point of choosing mathematics as a subject. Here is an opportunity for parents, teachers, and career counsellors to shift their own and their daughters’ perceptions of a woman’s place in fields requiring entry-level mathematics. – Kobus Maree, Faculty of Education, University of Pretoria
subject; it also opens an array of career opportunities, from astronomy through engineering to zoology. It’s still a common misperception that girls are at a disadvantage in understanding numbers and mastering the abstract thinking required. But research reveals no essential differences between girls and boys in terms of mathematical ability – and belief in the false stereotype can strongly inhibit female students’ success in mathematics. These are the chief findings of two 2006 articles in the journal Science. Janet Sibley Hyde and Marcia Linn2 reviewed over 100 different published studies of gender differences in mathematics performance, based on testing more than 3 million people. To compare male and female performance on a range of different tests, they computed the d statistic, which compares the mean for each group, in units of standard deviation. This unusually broad synthesis of studies revealed no gender differences in deep understanding of mathematical concepts at any age, nor any gender differences in complex problem-solving in elementary or middle school, although a small difference favouring boys emerged at high school. Moreover, whereas girls were found to outperform boys marginally on computation in elementary and middle school, there were no gender differences in high school.
Notes from TIMSS-R The results of the Third International Mathematics and Science Study – Repeat (TIMSS-R) (see box on page 38)*, which in 1998 assessed progress since the previous TIMSS study of 1995, showed that ■ in South Africa overall, there was no statistical difference in the maths scores between girls and boys (but, comparing all the provinces, girls did better than boys only in the Western Cape; the greatest gender gap was in the Free State and Mpumalanga, where boys scored 4–5% higher than girls) ■ internationally, there were no significant differences in maths achievement between girls and boys but inequalities may be shrinking; in 1995 boys scored significantly better than girls in 6 countries, whereas in 1999 the number of such countries had dropped to 3. * See analysis in S.J. Howie, “Third International Mathematics and Science Study-Repeat (TIMSS-R): What has changed in South African pupils’ performance in mathematics between 1995-1998?” (Available at http:// academic.sun.ac.za/mathed/amesa/TIMSSR. Accessed 22 July 2008.)
Quest 4(3) 2008 41
Careers in S&T Q Left: Applying the litmus test – using colour as an indicator of acidity (red) and alkalinity (blue) over the pH range 4.5–8.3 (at room temperature).
First computer programmer – a woman Charles Babbage (1791–1871) takes credit for the design of computer hardware, but his collaborator of several years, Ada Augusta, Countess of Lovelace (the only legitimate child of the poet, Lord Byron) was the pioneer of software. She wrote of herself: “I shall be a more famous programmer than my father was ever a poet.” Reported by Judy M. Bishop in “Computer programming: is it computer science?” South African Journal of Science, vol. 87 (1991), pp.22–33. ▲
maths performance was strongly linked to ‘stereotype threat’, defined as the phenomenon in which the awareness of a stereotype leads people to behaviour that is stereotype-consistent. In this study, females completed a maths test in two parts, with a comprehension test sandwiched in between. The test was on the topic of gender differences; one group received a text stating that there were inherent gender differences in mathematics ability in favour of males; another group’s text stated that these differences were socialized; a further group’s text stated that there were no gender differences in maths ability; and the final text simply mentioned gender without reference to mathematics ability. The first and last groups’ performances were significantly poorer than those of the two middle groups. In other words, when primed with the idea that males were inherently better at mathematics than females, or simply with the mention of gender, female performance was worse. The important message from this study is that it’s critical not to reinforce notions of sex differences in mathematical (or related) ability. If you believe you can do it, you probably can!
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To check further for gender differences in maths and science, Hyde and Linn compared performance in different countries. A study on fifthgraders’ performance on mathematical word problems in the USA, Taiwan, and Japan revealed much greater differences in performance among the different countries than among males and females in each country. This highlighted the role of cultural factors in determining performance – which can include the curriculum, time spent on homework, and parents’ beliefs in the importance of learning. What’s happening in South African schools? Our dismal overall participation rates in maths and science contribute to the skills shortage in technical professions. Influential commentators have suggested that we need, at the very least, to double the number of learners taking mathematics and science to be able to meet the country’s economic needs4. Almost the same numbers of female and male students in fact take matric mathematics, with similar pass rates overall5. Yet in the vastly different South African school contexts, girls in privileged schools are outperforming their male counterparts in maths, although in the poorest schools this picture is reversed6. Impoverished school environments can have a devastating impact on female learners’ chances of success in mathematics, but it is also possible to create conditions where girls can fulfil their potential. Improving the schooling of most South African learners could dramatically raise the participation rates of females in mathematically-based careers. – Éva Plagányi-Lloyd (Department of Mathematics and Applied Mathematics) and Jennifer M. Case (Department of Chemical Engineering), University of Cape Town; both are active members of South African Women in Science and Engineering (SAWISE)
Reading, maths, and gender equality Results of a study published on 30 May 2008 by Luigi Guiso of the European University Institute in Florence and his colleagues7 appear to reinforce the notion that girls are
better than boys at reading, but that the traditional gap in maths scores virtually disappears in societies with high levels of gender equality. Using data from the 2003 Organisation for Economic Co-operation and Development (OECD) Programme for International Student Assessment, where some 276 000 15-year-olds from 40 countries sat the same maths and reading tests, the researchers compared the results, by country, with each other and with various measures of social sexual equality (including the World Economic Forum’s Gender Gap Index, which reflects economic and political opportunities, education, and wellbeing for women; an index of cultural attitudes towards women; the rate of female economic activity in a country; and women’s political participation). On average, the boys did better than the girls in maths, but the gap was largest in countries with the least equality between the sexes, such as Turkey. It disappeared in countries such as Norway and Sweden, where the genders are more or less on a par with each other. The researchers ran a statistical check to make sure that the correlation was not generated by any further variable correlated with gender equality, such as GDP per person. They claim that their data show the closing of the gender gap in maths scores to be related not to economic development, but directly to improved social position of women. The single mathematical gap that did not change was the difference between girls and boys in geometry. This seems unrelated to gender equality, and the boys did consistently better. The gap in reading scores not only remained, however, but grew as the sexes became more equal! Average reading scores were higher for girls than for boys in all countries. But in more-equal societies, not only were the girls as good at maths as the boys, but their advantage in reading was greater. It seems that girls may acquire an absolute advantage over boys as a result of equal treatment – a point that society in general may have to come to terms with8. ■
4. Centre for Development and Enterprise, Doubling for growth: Addressing the maths and science challenge in South Africa’s schools (Centre for Development and Enterprise, Johannesburg, 2007). 5. V. Reddy, “Cross-national achievement studies: Learning from South Africa’s participation in the Trends in International Mathematics and Science Study (TIMSS)”, Compare, vol. 35, no. 1 (2005), pp. 63–77. 6. See M. Kahn, “For whom the school bell tolls: Disparities in performance in Senior Certificate mathematics and physical science”, Perspectives in Education, vol. 22, no. 1 (2004), pp. 149–156; and H. Perry and B. Fleisch, “Gender and educational achievement in South Africa”, Marking Matric: Colloquium Proceedings (2006). 7. L. Guiso, F. Monte, P. Sapienza, and L. Zingales, “Culture, gender, and math”, Science, vol. 320 (2008), pp. 1164– 1165. Reported in “Vital statistics”, The Economist, 31 May 2008 (pp. 91–92). 8. A new study, covering 7 million students doing standardized tests in 10 US States, indicates that girls are now scoring just as well as boys in maths. For details see J.S. Hyde et al., “Gender similarities characterize math performance”, Science, vol. 321 (25 July 2008), pp. 494–495.
Teaching and learning about shore ecology is best done where it’s all happening, advises Dumile Tshingana. He explains how a pilot educational outreach coastal monitoring programme in the Eastern Cape brings learners and teachers into direct, active contact with environmental science.
Out of the classroom, into the field
trampling, and indirectly through pollution and litter. In addition, climate change along this coastline could generate changes in plant and animal life. Monitoring the habitats within the coastal environment is therefore critical for evaluating their state of health. Our pilot outreach programme aims to start regional monitoring initiatives that can expand into other areas – as sites are identified, learners actively engaged, and terrain marked out for permanent long-term investigation. Curious learners will see the reality of what is happening in the coastal environment outside their schoolyards – and find out how to explore and address these realities for the rest of their lives. ▲ ▲
ssociated with the SAEON Elwandle (Coastal–Inshore) Node, or observation platform, is the pilot Schoolyard Long-Term Ecological Research (LTER) coastal monitoring programme. This outreach environmental science initiative gives students and educators the chance to experience at first hand – and make a real contribution to – the scientific processes used for monitoring and looking after South Africa’s coastal ecosystems. The shores and estuaries of the Eastern Cape are among the country’s most productive ecosystems. Despite their ecological significance and conservation status, however, they are being increasingly affected by people – directly by harvesting and
Photographs: Courtesy of SAEON
Top right: SAEON researchers take notes as they measure and monitor plants at a designated site. Right: Monitoring a coastal area.
Maths and environmental science Mathematics is a pervasive and essential instrument of environmental science. Conservationists rely on maths to help to interpret and explain what their observations of environmental conditions mean. They need, for example, to count the different animals in a nature reserve so as to prevent overstocking that would cause starvation and death, turning the reserve into a desert. But animals differ in size and in what they prefer to eat. They are also hard to count because they can hide, run, or swim away, and counting them from a helicopter or boat costs a lot of money. Imagine trying to count many different kinds of fish that can swim underwater anywhere they like*! So scientists use mathematics to estimate numbers and work out what there is per separate area; and also to calculate whether there will be enough food for the animals, how many may be hunted or fished, and even how many there will be next year. The data are often integrated in graphs and maps, to allow visual comparisons of places, species, conditions, and times. Mathematical formulae are used to establish future conditions, so that the right decisions can be taken early enough. And mathematical models are constructed from massive amounts of data, which often represent complex ecological interrelationships, and must therefore be analysed through computer programs and statistical methods. – Johan C. Pauw, Managing Director: SAEON * For ways in which scientists approach this problem, read “Still counting” in Quest, vol. 3, no. 1 (2006), pp. 24–27.
SAEON The South African Environmental Observation Network (SAEON) was created to deliver long-term reliable data for scientific research and for informed management and policy-making. Its six nodes cover various ecosystems (Savanna; Arid Lands; Fynbos; Marine–Offshore; Coastal–Inshore; and Grasslands/ Forests/Wetlands), with a connecting internet datamanagement system. Earth observation monitors the planet’s surface from space by satellites, from the air by cameras, and from the ground by direct measurements. To determine real trends and changes – given the variability and complexity of natural systems – SAEON keeps environmental data over many decades. South Africa co-chairs the Group on Earth Observation, which is developing a Global Earth Observation System of Systems into which SAEON data will be fed. As a network of organizations and people involved in environmental observation, SAEON integrates the work of different research organizations and people. It also promotes the development of young scientists by supporting science and mathematics educators, learners, and students through environmental monitoring and research projects. – Johan C. Pauw For more about SAEON, visit www.saeon.ac.za. For an impression of issues covered by SAEON, consult the special suite of articles in the South African Journal of Science, vol. 103 (2007), pp. 289–342.
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Careers in S&T Q
Above and right: Taking samples and measurements on land and at sea.
Schoolyard programme participants examine the rocky shores. Photograph: D. Tshingana
Why monitor rocky shores, sandy shores, and estuaries? These ecosystems support some of South Africa’s richest and most diverse coastal plant and animal life (biota), yet they are subject to constant change, mainly through people. At some sites, especially in the Eastern Cape, harvesting and trampling have dramatically reduced the abundance and diversity of the biota (mussel harvesting, for example). The accessibility of these ecosystems has encouraged more and more visitors of various kinds. But walking along the rocky shores and estuaries can disturb some species and lead to unpredictable changes. By their nature, rocky shores, sandy shores, and estuaries are exposed to many of the pollutants produced by human (anthropogenic) activity. Contaminants released into the air fall on the sea surface, and they are carried onto the shore – as also are chemical contaminants, such as oil spills from ships. Waste materials dumped on land are washed into the sea, some remaining for years on the coast that they cross. The animals and plants that inhabit coastal areas may be affected more seriously by anthropogenic activities than biota in the sea elsewhere. But the accessibility of these habitats can make them easier to monitor and observe, so they make fine outdoor marine classrooms. Scientists predict that, with rising air and sea temperatures, the distribution of species along our coast is likely to change, and global warming will probably cause water levels to rise. The zonation pattern of the intertidal area, where species are sorted into bands according to tidal height, may be particularly sensitive to such adjustments, as a rise in sea level could shift the zones higher up on the shore, and also change the pattern itself as the shoreline configuration and associated wave-forces alter over time. Long-term, annual sea-level cycles could also influence zonation patterns. For these reasons the SAEON Elwandle Node emphasizes the importance of observing and tracking marine organisms over time, and actively engages young people in this exercise.
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Real participation Through the Schoolyard programme, students actively participate – as part of the Rocky Intertidal Monitoring Project – in surveying key invertebrate and algal species at one of the established rocky-shore monitoring sites in the Bushman’s River mouth. They examine marine life and tidal patterns; identify fish and other marine organisms in the rocky shores; test the estuary water’s pH (acidity or alkalinity) and salinity; and analyse its turbidity (the sediment that it carries). Intertidal monitoring is conducted at low tide; and transects and quadrats1 are used to survey and measure the abundance, distribution, and speciesrichness of the area. The programme targets Grades 9, 10, and 11, and the three participating schools are Ikamvalesizwe Combined School and Nompucuko Combined School in Kenton, and Kuyasa Combined School in Port Alfred. Participation in a hands-on outreach programme such as this one offers in-depth, experiential learning2. It is a practical way to start to understand the ecology of one of the world’s most diverse ecosystems, with its rocky intertidal habitats, estuary, and sandy shores. Research-based monitoring helps students to develop problem-solving skills, use the tools and methods employed by field scientists, and learn to analyse data. Students also make their own active contributions to a data-set used to identify changes in the life of these ecosystems over long periods of
time. This project incorporates natural science, life sciences, physical science, and mathematics, through curriculumdriven activities addressing national educational requirements. In the classroom, before going into the field, students find out about the Schoolyard programme; learn the importance of monitoring; learn to identify the organisms that are surveyed in the field; and practise protocols of monitoring using graphs, field guides, quadrats, and learner-support materials such as posters and textbooks. Back at school after field expeditions, students work with the data they have collected, generate graphs that can be used to interpret results, and share their findings through presentations and poster demonstrations. The Schoolyard monitoring programme provides long-term data. What’s important is that it also introduces learners to the rich coastal biota, and builds up a group of informed, concerned citizens who will continue watching over and nurturing these fascinating ecosystems in the future. ■ Dumile Tshingana is an environmental educator, based at the SAEON Elwandle Node in Grahamstown. For information about the Schoolyard (LTER) programme, contact Dumile Tshingana, SAEON Elwandle Node Education Outreach, Somerset Street, Private Bag 1015, Grahamstown, 6140, or e-mail firstname.lastname@example.org, or visit www.saeon.ac.za. For more on SAEON’s outreach programmes, contact the SAEON Education-Outreach Coordinator, Ms Sibongile Mokoena, by phone at (012) 392 9379 or by e-mail at email@example.com
1. A transect is a sample strip of land used to monitor plant distribution, and animal populations, for example. A quadrat is an area of vegetation, usually one square metre, selected at random for the study of plants in the surrounding area. 2. In the planning stages is another project to monitor coastal weather. Participating schools will conduct continuous weather observations. The project will largely depend on the availability of weather observation kits and data collection tools. Learners and educators will collect data over time until they see the weather trend (or overall picture of coastal weather fluctuations). These data will be translated into school syllabus work through graphical interpretation and charts.
Q Careers in S&T
The why (and how) of biomaths
athematical models in biology? No, they’re not photoshopped superstars on the catwalk (or greybeards), nor tiny triangles, cleverly made. Like any mathematics, they are devices to help us to understand things better. Models in biology need not be mathematical. Consider the most important one of all: Darwin’s theory of natural selection. The little bit of mathematics in his conception of “the struggle for existence” is soon lost in metaphor and long catalogues of fact. That was his debating style: in presenting his case for evolution in On the Origin of Species (1859) he devotes more space to possible arguments against his theory, in fact, than to its details. In the last 100 years or so, however, mathematics has clarified and supported Darwin’s original thinking. Mathematical models of genebased inheritance of traits have helped to elucidate and even settle many of his points. In presenting them, he earned our great admiration, both for his deep understanding of the difficulties of the theory, and his honesty in dealing with them. Any model involves abstractions. Darwin’s “struggle for existence” is a good example. We biomathematicians try to describe these abstractions in mathematical terms. The process of turning vague ideas into rigorous mathematics can be difficult, even painful. It may be that the original model becomes unrecognizable, or trivial, or obviously wrong. But searching tests of this sort are good for science. Mathematics is also profoundly creative – once we have constructed a mathematical model, we can tease out its implications tremendously far and trace its connections with other models in great depth. In the field of biology, models have played a big role in the study of cellular processes, whole-organism physiology, individual behaviour, ecological interactions, and much more. South African biomathematics is alive, and as well as can be expected. With more funding and more postgraduate students, it can do even better! Here are a few examples from a recent conference that showcased some of our work**. ■ A careful estimate of the impact of
Biomathematical* models are tools for describing the world of living organisms in nature in a way that helps us to understand them better, collectively and individually, explains Henri Laurie. poaching on perlemoen (abalone) on South Africa’s south coast (in the paper by Charles Edwards & Éva Plagányi). Such assessments are tricky because there are so few reliable data, but they are essential if any effort to improve the situation is to be based on something better than guesswork. ■ A review of simulated motion in groups of animals (Christophe Lett and Vincent Mirabet). These days, modellers focus on groups as collections of individuals. The resulting models require lots of computation, but achieve realism with extremely simple rules for how individuals change direction and speed. ■ An investigation into the effect of various types of treatment on HIV in a patient (Rachid Ouifki et al.). The task here is extremely difficult: the dynamics of HIV in the human body are not fully understood; it is hard to know, for particular individuals, exactly where they are in the disease process; our data accumulate slowly because the disease progresses so slowly under treatment. Nevertheless, models make possible the mathematical study of various modes of therapy. The advantages are that one gets results quickly (clinical trials take years) and no patients are directly endangered (although misinterpretation of models is always dangerous). ■ News about measuring accurately the progress of the HIV epidemic (Alex Welte). It had been hoped that the common test for diagnosing infection could reveal the rate at which new infections are occurring. But there’s a short ‘window period’ (the time between infection and detectable levels in the blood) during which diagnosis is impossible. Welte shows that an accurate estimate of the rate of new infections is more difficult with shorter window periods. This unwelcome
surprise is not unlike the problem of measuring the speed of a car by timing it over very short distances – one needs very accurate measurement of the elapsed time! To overcome the problem of accuracy, he suggests that a less sensitive test with a longer window period may be used. Of course, this would be additional to the sensitive test, which is still essential for early detection. Although technical research papers are not easy reading for a non-specialist, mathematics brings practical rewards when it is applied to real-life problems. It’s also very rewarding in itself, if you’re willing to make the effort and devote time to the material at hand. Because mathematics is a tool for working with abstractions, it means going through the steps methodically and carefully to reach reliable conclusions. Jumps and sudden insights are rare. A useful approach is to build on your own current understanding of a problem: ■ look for signposts – the central formula, the one or two definitions that are most important ■ look for the logic – outline the main steps ■ look for help from outside – supply your own examples, find similar ideas in slightly different contexts, talk to someone who shares your interest ■ repeat, reapply, and refine the processes. When to stop? Ideally, when the full structure of the reasoning is clear to you! – Dr Laurie is in the Department of Mathematics and Applied Mathematics at the University of Cape Town. ■ * Biomathematics (biomaths) is the field of mathematics dealing with issues related to biology. ** A suite of research articles from this conference, including the four papers cited here, appeared in the South African Journal of Science, vol. 104 (May–June 2008), pp. 172–220.
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Not just elephants at Addo Megan Bradfield recommends a visit to the Addo Elephant National Park in the Eastern Cape for an amazing variety of wildlife, ecosystems, and landscapes. Top: Addo elephants at a waterhole, cooling themselves with water and mud. Photograph: Piet Heymans
Below: The coastal area of Addo Elephant National Park at Woody Cape. Photograph: Courtesy of the Addo Elephant National Park
lephants and flightless dung beetles – and many wonders in between, inland and along the coast – await visitors to Addo Elephant National Park. Its 168 000 hectares stretch across five of South Africa’s seven biomes, from the vast Darlington Lake in the arid Nama Karoo, across the Zuurberg Mountains covered in fynbos and grassland, through the dense thicket of the Sundays River Valley, to the lush green indigenous forests at Woody Cape, which hug the largest coastal dune fields in the Southern Hemisphere. The park was first proclaimed in 1931 to save the few surviving elephants of herds decimated by hunting, the ivory trade, and clashes with farmers. Today, it covers nearly 85 times its original size. Its emphasis has shifted to the goal of conserving the entire area’s unique and varied biodiversity – and it’s a treasure-trove for conservation research. Curious habits of flightless dung beetles King of the roads in the park is the flightless dung beetle (Circellium bacchus), which occurs
only in this area and enjoys special protection. Signs warn visitors not to drive over it, or over the scatterings of elephant dung that often conceal dung beetles at work. This beetle faces daily hazards – tourist cars; predation by ostrich, jackals, and meerkats; and the limitations of its physiology. Most dung beetles use flight and their own terrestrial activity to warm themselves up (that is, they produce heat endothermically). The flightless dung beetle possesses only vestigial wings, having probably lost the ability to produce heat endothermically through atrophy of the flight muscles. This makes it particularly susceptible to temperature, so it’s most abundant when the temperature is mild and the conditions moist. Having has lost the ability to fly, this beetle has evolved a method to survive in arid environments. Its tightly-sealed elytra (wing case) forms a cavity where the wings would normally reside, and it breathes by pumping air in and out of its body through small valves called spiracles. But when these valves are open, the beetle can lose valuable water by evaporation. It breathes air in and out through the spiracles at the front of the body, lifting the elytra to release the carbon dioxide Did you know? The Addo Elephant National Park is sanctuary to more than 480 elephants, as well as buffalo, spotted hyenas, zebra, antelope, reptiles, amphibians, insects, and more than 400 different types of birds. It boasts the Big Seven (elephant, rhino, lion, buffalo, leopard, southern right whale, and the great white shark); protects the world’s largest Cape gannet breeding population on Bird Island; and conserves endangered and vulnerable species, including the black rhino (Diceros bicornis bicornis), Cape mountain zebra (Equus zebra), tree dassie (Dendrohyrax arboreus), oribi (Ourebia ourebi), blue duiker (Philantomba monticola), leopard (Panthera pardus), lion (Panthera leo), and dune cycad (Encephalartos arenarius).
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Q The S&T Tourist
Above: The Zuurberg mountain range in Addo Elephant National Park. Above right: Flightless dung beetle pair, engaged in rolling a dung ball. Right: King (and queen) of the road.
Photograph: Anthony Hall-Martin Photograph: Courtesy of the Addo Elephant National Park
Photograph: Piet Heymans
waste. There is therefore a time when this gas builds up in the cavity, allowing the beetle to exhale less often and hold its breath for longer. The high concentration of carbon dioxide in the cavity draws in oxygen, reducing the time that its spiracles are open to the environment and in this way minimizing water loss. The male beetle makes a ‘nuptial’ ball of dung, which he rolls away, with the female following. En route, he may have to fight other beetles wanting to steal his hard-earned ball. He buries it, and the male and female mate inside the hole, afterwards eating the ball, which can take several days. The female then prepares and buries a brood ball. She enters the hole alone, makes a hollow on one side of the ball, and lays a single egg, after which she leaves the hole, closing it up behind her. A week later, the white grub larva hatches and eats the ball from the inside. Its outer shell hardens, preventing the dung from drying out. After two to three weeks, the larva has eaten all the dung and, inside the hollow shell of dung, forms a pupa, which then pupates into an adult beetle. More about elephant and rhino Addo has probably the world’s most comprehensively recorded elephant population. Since 1976, individuals’ photographic identification files have been compiled, with data on sex, age, development, and social behaviour. Association patterns have been observed, showing which elephants belonged to which family group and which calves belonged to which cows; maternal family trees dating back to the creation of the park in 1931 have been reconstructed; and researchers have been looking into population genetics and paternity. Research on the impact of Addo’s megaherbivores on thicket vegetation has been particularly interesting, with data stretching back to 1974 showing loss of plant species (particularly among the small, largely endemic succulents and geophytes) and a decline in plant biomass in the
area containing elephants. High elephant density increases the number and size of paths through thicket. As these paths widen, the proportion of open habitat increases and microclimates change, with air and soil temperatures of such open habitat becoming more extreme than in intact thicket – and with implications (as yet unknown) for plant and animal physiology, and seedling germination and survival. The black rhinoceros (and probably other browsers) is also affected. Elephant paths initially give it access to the forage along the edges of thicket patches, but subsequent dominance of the landscape by the paths leads to loss of such feeding opportunities. Most recently, researchers have been using dung analysis for a clearer picture of the Addo elephants, as it gives information about an individual’s sex, DNA, reproductive status, stress levels, diet, and general health. It’s a method also used to investigate the park’s often elusive black rhino population, to help in monitoring the health and reproductive status of this critically endangered species. What’s new South African National Parks conserves systems in a way that is as natural as possible, introducing only those species that historically belonged in the area. This explains the reintroduction in 2003 of lions and spotted hyena into Addo after more than a century of absence. New expansions link Addo’s terrestrial and marine environments, after the Woody Cape area was incorporated (in 2002), Bird and St Croix Islands were proclaimed (in 2005), and a new, large Marine Protected Area of about 120 000 hectares proposed in Algoa Bay. There are ever increasing opportunities to get to know and enjoy nature’s diversity at Addo! ■ Megan Bradfield is the Communications Manager: Frontier Region at South African National Parks.
What to do and where to stay To enrich your stay, there are guided game drives, self-drives in the wildlife area (with the option of hiring a hop-on guide), guided horse trails, and a trail for 4×4 vehicles. Hiking trails include a wheelchair-friendly one, short trails in the Zuurberg Mountains, and the overnight Alexandria Hiking Trail in Woody Cape. At Addo Rest Camp, there are different types of self-catering accommodation (and a swimming pool for guests), a restaurant open from early until late, a shop, a fuel station, and a postbox. You can also stay at the new Camp Matyholweni, close to the beach and the Sundays River Mouth; Narina Bush Camp in the foothills of the Zuurberg Mountains; and at your choice of five-star private lodges within the park, each with its own unique experience to offer. For more information about Addo Elephant National Park, visit www. sanparks.org/parks/addo, or phone (042) 233 8600, or fax (042) 233 8643, or e-mail firstname.lastname@example.org
Quest 4(2) 2008 47
Right: A child in Kenya helps with building a hospital. Middle: Children selling fire crackers at a market on the occasion of Diwali, in Chennai, India. Far right (opposite page): Houses in most Indian villages do not have piped water facilities. All members of the family have to do their bit to get the day’s water requirement. Here, two girls carry vessels filled with water from the lake to their home, which is about a kilometre away.
“Child Labour” The 2002 report of the International Programme for the Elimination of Child Labour* comments that not all children’s work is harmful, and it defines what is to be abolished. ‘Child labour’ slated for abolition falls into three categories: (1) Labour that is performed by a child who is under the minimum age specified for that kind of work (as defined by national legislation, in accordance with accepted international standards), and that is thus likely to impede the child’s education and full development. (2) Labour that jeopardizes the physical, mental or moral well-being of a child, either because of its nature or because of the conditions in which it is carried out, known as hazardous work. (3) The unconditional worst forms of child labour, which are internationally defined as slavery, trafficking, debt bondage and other forms of forced labour, forced recruitment of children for use in armed conflict, prostitution and pornography, and illicit activities. This remains the official policy of the International Labour Organization (ILO). There is no controversy over number (3), although there is not always agreement about effective ways to prevent the worst forms of child exploitation. Nor is there disagreement about (2), provided it is understood that conditions can sometimes be improved. Regarding number (1), it is agreed that children’s labour should not be allowed to impede a child’s education and full development. The question is whether all work performed by a child who is under the specified minimum age has damaging effects – especially in the many cases worldwide where the child is already out of school. In 2000, South Africa ratified the ILO’s Minimum Age Convention, which is the basis for international standards and which forbids admission “to employment or work in any occupation” of a person under the age of 15 (or 16 or 14 in some countries), unless specifically allowed as “light work” for children not more than two years under the minimum age. “Work” includes economic activity whether or not it is paid employment. By these standards, in South Africa today, if a child under the age of 13 helps parents in any commercial enterprise for as little as an hour a week, this is classified as “child labour”. In other words, anyone aged 12 or younger helping mother with chickens for sale, would technically be a “child labourer”. The term ‘child labour’ thus includes work that may be beneficial rather than harmful; yet it has extremely negative connotations. I therefore avoid the term. When I discuss work that is harmful or hazardous, I say “harmful work” or “hazardous work”. I want to eliminate the harm and the hazards, but not necessarily the labour. * International Labour Organization, I.P.E.C. Action Against Child Labour: Highlights (ILO, Geneva, 2002, p. 9, section 26).
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How bad is The International Labour Organization (ILO) is campaigning to abolish ‘child labour’ worldwide. Considering the evidence, Michael Bourdillon argues that the answer isn’t quite so simple if what’s best for children is really what we’re after.
ow does it happen that wellintentioned attempts to protect children from abusive labour can often leave the disadvantaged children even worse off than before? Or that policies put in place to help people can sometimes turn out not to be in their best interests after all? One answer lies in the way that evidence is put together and put into practice. In the physical sciences, we believe that, in the long term, what’s based on evidence will prevail. In the social sciences, clear verification from evidence is often more difficult. Nevertheless – in an ideal world – we would expect policies to be based on the findings obtained from research. We would expect interventions to be carefully evaluated to ensure that they have the desired effects, without too many serious and unintended costs. In reality, political agendas and the interests of powerful people – disguised as moral principles – often override available evidence of flaws in policy. International strategy on ‘child labour’ is an example of this phenomenon. Many well-meaning middle-class people regard terrible conditions of working children as part of a horrific European past, before public social conscience brought things under control. Now we have reports of young children starting work before the age of ten, spending long hours in gruesome conditions, with little or no time for schooling or leisure, in perhaps a carpet
or silk industry in Asia, or on cocoa farms in Africa. Horrified, we insist that such cruel treatment of children must cease at once. So a campaign has developed to ‘stop child labour’, in which the public is becoming more and more involved. It is supported by genuine human concerns about the treatment of children. Opposing such a campaign seems at first sight unthinkable. Perception vs evidence Sensational accounts of abused children draw attention to the urgent need for intervention, but they rarely provide enough information about the backgrounds of the children and their families to make sure that their situation is thereby improved. There is growing evidence to suggest that talk of ‘eradicating child labour’ in fact fails to protect children. Rather, it restricts opportunities for children in both wealthy and developing communities, and often damages the livelihoods and wellbeing of poor children. Yet public reaction is largely ignorant of such research, inflamed instead by reports and TV footage of extreme cases of the mistreatment of children. Policy on this issue has been driven largely by the mandate of the International Labour Organization (ILO) to work for the abolition of ‘child labour’ when the organization was established in 1919. The main aim has been to exclude children
‘child labour’? Misplaced outrage In the early 1990s, the media reported on girls travelling far from their homes to work long hours – even late into the night – amid squalor in prawn-curing factories in Kerala, southern India. They were said to have been locked up to sleep in a single hall without beds. The reports aroused moral indignation and condemnation by activists. The Dutch anthropologist, Olga Nieuwenhuys, interviewed some of the girls in their home village, and met a different perspective*. They described their struggle to persuade their fathers to let them travel with their friends, against the cultural norms of their communities. They enjoyed the journey away from home, as they did the video entertainment on weekends at their destination.
below a certain age from economic activities and from the workforce. But policy appears also to be influenced by underlying vested interests1, and fears that employment of children could threaten the jobs and wages of adults in the developed world. What does research tell us about children and work? The idea that childhood should be a time for school and play, without responsibility or serious work, is a cultural phenomenon that grew up in the middle classes of Western Europe and North America. But nowhere has this been proved to be the best way of preparing children for adulthood in societies in the developing world that have few material resources – nor indeed in any society. Viewing work as bad for children takes away intrinsic value from their activities. This attitude treats them as totally dependent on their elders, and leaves them to do little for themselves. It also ignores the substantial ways in which children often contribute to their communities2. This western approach to childhood relates to an idea that children need to be moulded by adults into the values and culture in which they
They wanted to earn as much money as possible while they were away, and were paid on a piece-work basis, so they wanted to work long hours. They found the dormitory a congenial and safe place to sleep. They escaped much unpaid work and drudgery at home. The money they earned brought them status and contributed to their dowries, which improved their chances of a good marriage and a better future. The moral indignation at their exploitation in these factories appears, on the evidence, to have been seriously misplaced. * For details, see O. Nieuwenhuys, “The household economy in the commercial exploitation of children’s work: The case of Kerala”, in B. Schlemmer (ed.), The Exploited Child (Zed Books, London and New York, 2000), pp. 278–291.
Bangladeshi garment industry In 1992, Senator Tom Harkin introduced a bill in the US Congress to ban imports of goods produced with ‘child labour’. Although the bill was never passed, an estimated 50 000 children may have lost their jobs in clothing factories in Bangladesh. The authorities in that country were aware that this would damage the children, but they could not afford risking their main export industry and putting even more thousands out of work. Initially, none of the sacked children went to school. Many found jobs in which pay and conditions were worse than before. After massive input of funds from international donors, about 30% of the children who had been dismissed eventually received some schooling, often in special schools established to accommodate them*. Now the project and funding have dried up, as have the special schools. Fewer children are employed in formal factories, and nothing is being done to help the families of younger children, who might have benefited from being able to earn. * UNICEF, Assessment of Memorandum of Understanding (MOU) regarding Placement of Child Workers in School Programmes and Elimination ofChild Labour in the Bangladesh Garment Industry (1995–2001) (UNICEF Regional Office for South Asia, Kathmandu, 2003).
live. Children in fact contribute to the shaping of culture, sometimes in cooperation with adults, but often on their own when adults fail to cooperate with them – through youthgang culture, for instance. Children constantly respond to their social and material environment, and are active agents in their own development. Arguments for banning ‘child labour’ are frequently based on the assumption that, if not allowed to work, children will go to school. In reality, children often start working only when the
1. For details, see M. Woodhead, “Developing policies on child labour: has research made a difference?” in K. Engwall and I. Soderlind (eds.), Children’s Work in Everyday Life (Institute for Futures Studies, Stockholm, 2007), pp. 15–26. 2. See V.A. Zelizer, Pricing the Priceless Child: The Changing Social Value of Children (Basic Books, New York, 1985). 3. Several studies in Britain, USA, and the Netherlands show that the majority of young people acquire experience of part-time work before they leave school.
schooling system has failed them, because it is inaccessible, or expensive, or ill adapted to their needs and interests – sometimes even humiliating and psychologically damaging. When such children are prevented from working, they rarely end up in school unless the right schools are specifically made more accessible to them. Then, the evidence suggests, children usually choose to attend school, and drop or decrease other work without the necessity of a ban. In both rich and poor countries, a majority of adolescents prefer a combination of work and school3. Furthermore, it has not been shown to be generally true that child work
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Top: Young boy hauling water to the family house. No water tap in the vacinity. Above: A child learns a job in a workshop. ▲
threatens adult jobs and brings down wages4. But even where this may happen, improved adult wages are not always used to benefit children. More broadly speaking, it is not necessarily to the advantage of children to make it illegal for them to work. They often have to earn to be able to afford to continue going to school! Many of them (in particular, orphans, refugees, or those fleeing abuse or destitution at home) have no adult support. They are marginalized even further if society discriminates against them by forbidding them to earn an honest living. When ‘fair trade’ asserts that the goods they recommend involve ‘no child labour’, is this fair to children who genuinely need to earn?5 In many societies, including indigenous South African ones, children are traditionally given responsibility – and work to do – at an early age, such as caring for younger siblings and,
Banning child domestic employment in India Poor children in developing countries are widely employed in domestic work for wealthier families. Because it is similar to what children do in their own homes, this kind of work often escapes the attention of campaigns against ‘child labour’. In practice, children employed in domestic work are widely abused in a variety of ways: hours are long with no formal time off or holidays; wages are low; living conditions are poor; child workers are often away from home, with restricted access to family and peers; they are frequently denigrated, resulting typically in low self-esteem; they are vulnerable to physical and sexual abuse. In response to pressure, the Government of India banned the employment of children under the age of 14 in domestic or related work, effective in October 2006, under the provisions of the Child Labour (Prohibition and Regulation) Act, 1986. This was widely acclaimed as a step forward for children’s rights. Yet certain NGOs in India pointed out that the ban put half a million children summarily out of work and that even six months later virtually nothing had been done to support them. At the time of the ban, a boy about 12 years old attending an international meeting of working children in Italy explained that he had left the poverty of his rural community to earn a living collecting rags in Delhi. There he learned how to make tea, and improved his situation by working for a tea shop. He described his day: he got up at four to open the shop. After his tea round, he had breakfast and went to school. In the afternoon, he returned to the shop. He did his school homework at a support centre in the evening, and collected the shop keys from his employer before going to bed. Occasionally he could visit home with small presents for his family bought with his earnings. He commented, “I don’t know what I shall do when I return with this new law. Perhaps I can find work at night or somewhere where I can’t be seen.” This boy needed support, but he did not need his source of livelihood to be taken from him without its replacement with something better. To add insult to injury, this kind of ban does nothing to protect the very many children who have excessive work imposed on them within their own families.
in agricultural communities, helping with crops and livestock. As children grow, this practice extends to other family enterprises and even to paid employment, with children’s earnings contributing to the family’s livelihood. Work gives children status and respect in their own communities, and often among their peers. Many studies have shown that work – including waged work – is beneficial to the development of adolescents, and even of younger children, teaching skills that are necessary for life and not learned in formal schooling. What’s the answer? Stopping children from working and punishing employers can benefit children labouring in extremely abusive conditions, provided the intervention includes tangible, practical, and sustainable support for the young people. Nevertheless, it is not clear that enforcing existing legislation that bans ‘child labour’ will generally benefit working children: the vast majority of them need protection not from work but in their work – they need better wages, shorter hours that do not interfere with schooling, safer and better working conditions, and security from unjust dismissal. No such protection is offered by interventions that remove children from employment. On the contrary, minimum-age legislation increases their fear of losing their jobs, and often
4. Few studies have examined the effects on adult wages of stopping child labour, and the results have been mixed. A study in Mexico, for example, suggested that removing children from the labour market increased adult wages, but not enough to make up for the lost earnings of children (E.V. Edmonds, “Child labor”, in T.P. Schultz and J. Strauss, J. (eds), Handbook of Development Economics, Elsevier Science, Amsterdam, 2008). On the other hand, a study in Egypt found the work of children to compete modestly with the work of women and to complement the employment of men; for the society as a whole, the work of children did not appear to affect adult employment (Charles Diamond and Tammy Fayed, “Evidence on Substitutability of Adult and Child Labour”, Journal of Development Studies, vol. 343(3) (1998), pp. 62–70). 5. Fairtrade International insists on no employment of children under the age of 15, irrespective of the fact that in some countries this is not illegal.
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drives their work underground, where it becomes more exploitative and abusive than legal work in regulated formal employment. Such legislation offers no protection to children (including many in South Africa) whose schooling and development is undermined by excessive work in their own homes – sometimes essential work, such as caring for sick parents. In the real world, children and their families make choices that are based on what is available to them. To improve the situation of children, societies (and legislators) need to make better choices available, rather than taking away from people in need the option that appears to them to be the best they have. ■ Professor Bourdillon is a social anthropologist who taught in the Department of Sociology, University of Zimbabwe, for over 25 years. For the last ten years, he has researched and written about children’s work in Zimbabwe and elsewhere, and worked with several organizations supporting working children. He wrote this article while a fellow at the Netherlands Institute of Advanced Study. For more on ‘child labour’ in southern Africa and elsewhere, read J. Boyden, B. Ling, and W. Myers, What Works for Working Children (Rädda Barnen & UNICEF, Stockholm, 1998); G. Clacherty, “Report on a Children’s Participation Process: Towards a South African Child Labour Programme” (Department of Labour, Pretoria, 2002); B. Hungerland et al. (eds.), Working to be Someone: Child Focused Research and Practice with Working Children (Jessica Kingsley, London and Philadelphia, 2007); L.E. Bass, Child Labour in SubSaharan Africa (Lynne Reiner, Boulder and London, 2004); M.F.C. Bourdillon (ed.), Earning a Life: Working Children in Zimbabwe (Weaver Press, Harare, 2000); and S. Levine, “Bittersweet harvest – Children, work and the global march against child labour in the post-apartheid state”, Critique of Anthropology, vol. 19(2) (1999), pp.139–55. Visit www.workingchild.org/; www. ilo.org/ipec/index.htm; and http://eja.enda. sn/page%20anglais/indexanglais.htm.
Q Q UEST crossword You’ll find most of the answers in our pages, so it helps to read the magazine before doing the puzzle.
You + Science = Planet Earth : A better place to live! At Stellenbosch University’s Faculty of AgriSciences you will learn how to apply your knowledge of science to the benefit of both people and the earth.
Inactive; biological activity suspended (7)
No longer existing (7)
State of wellness (6)
Rubble; accumulated fragments of rock (6)
Widely encountered disease (8)
Down Fibrous protein, which forms a network that traps red cells and platelets (6)
Substance that can be metabolized to give energy and build tissue (8)
Our degrees take three or four years to complete. After a bachelor’s degree, you can broaden your career opportunities through postgraduate study.
Characteristic of or prevalent in a particular environment (7)
● A National Senior Certificate (NSC) as certified by Umalusi with an achievement of at least 4 in four designated university entrance subjects. ● An achievement of at least 50%, calculated in a ratio of 40:60, for the SU Access Tests and the average (excluding Life Orientation) obtained for the NSC. ● Mathematics 4, Physical Sciences 4 OR Physical Sciences 3 and Life Sciences 4.
A natural satellite (4)
Carbonaceous by-product of fire (8)
A disease-producing bacterium (8)
Wing case of the dung beetle (6)
Living tissue transferred from an organism to a culture medium (7)
Heavy radioactive element, used for dating and energy production (7)
A metabolic disorder, marked by excessive sugar in the blood and urine (8)
Setswana word, meaning ‘help’, given to a study of diet (5)
Greek prefix meaning ‘blood’ (4)
Intermediate stage of a beetle that occurs between the larva and the imago (4) Condition caused by lack of iron (7)
(Answers on p. 57)
South Africa needs well-trained agricultural and forestry experts at all levels to supply our growing population with food and fibre, to ensure that food and food sources are unpolluted and safe, and that the environment is used and managed in ways that preserve it for posterity.
Metallic element with magnetic properties, crucial for blood formation (4)
Site of the largest coastal dune field in the southern hemisphere (4)
The ‘L’ in the non-governmental organization ILO (6)
Sweet liquid secretion that is attractive to pollinators (6)
A citrus fruit (5)
‘Child’ in Setswana (4)
Magma or molten rock (4)
There are wide-ranging and challenging job opportunities in agriculture and forestry, from the most practical to the most high-tech – outdoors, in laboratoria, or in business.
Agricultural and forestry education Admission requirements
Exciting careers to consider after finishing your degree at Stellenbosch University ● Conservation ecologist ● Winemaker ● Forester ● Eco-tourism operator ● Entomologist ● Viticulturist ● Entrepreneur ● Community developer ● Animal or plant geneticist ● Horticulturist ● Wood processing specialist ● Quality controller
● Agricultural economist ● Researcher ● Environmental impact assessor ● Plant pathologist ● Extension officer ● Food scientist ● Animal scientist ● Soil scientist ● Consultant ● Water research manager ● Game ranch manager
Closing date for applications: 30 October 2008 Contact our Faculty Secretary (Leon Jordaan) at (021) 808 4833, fax (021) 808 3822, or e-mail email@example.com for more information and visit http://www.sun.ac.za/agric
Land, air, and the cosmos Aloes in Southern Africa. By Gideon F. Smith and Braam van Wyk. (Struik, 2008). ISBN 978 1 77007 462 0 This book presents aspects of the genus Aloe and its kin, the sturdy plants characteristic of the African savanna (bushveld) and karroid landscapes. Written for the interested lay person, amateur, school learner, aloe enthusiast, gardener, horticulturist, landscaper, and taxonomist, it introduces the natural habitats of these plants, offers suggestions for anyone wanting to grow and propagate them successfully, and includes a section on their uses as foods and medicines – including an aloe jam recipe put together by Braam van Wyk from first-hand experience. The rationale, explains Gideon Smith, was “to communicate the biology of the plants, and to tell (some of) their stories – how they deal with cold, how old they grow, what effect fire has on them.” The book
Spotter’s Guide: Birds of the Bushveld. By S.C. Kidson and H.L. van Niekerk. (Briza, 2007). (Also available in Afrikaans.) ISBN 978 1 875093 88 5 Bird Calls for Beginners. CD (bird call recordings) and book by Doug Newman. (Struik, 2008). ISBN 978 1 77007 678 5 What’s that Butterfly? A Starter’s Guide to Butterflies of South Africa. By Steve Woodall. (Struik, 2008). ISBN 978 1 77007 486 6 The Spotter’s Guide: Birds of the Bushveld is a small, neat, portable, practical, well illustrated, attractive field guide, with descriptions of 427 regular and 41 visiting bird species, and organized according to the birds’ outward appearance for easy reference. It focuses on the geographical area of the Limpopo Province, with its savanna punctuated by woodland-fringed riverbeds, rocky outcrops, and mountain ranges. Because this condensed guide is created for this particular region, the reader is saved the frustration of having to work through the far greater number of species than is necessary, as featured in more comprehensive field guides that include the entire subregion. It’s a perfect travelling companion for visitors to northern South Africa. Bird Calls for Beginners introduces 60 southern African birds by their characterisitic sounds. The slim accompanying handbook gives brief information to help a lay person to recognize the birdsongs and link them with the appearance and location of the singers. Distribution maps give an idea of where the birds may be found, with icons offering basic food and nesting information, together with a description of the call of each bird and the corresponding
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covers about half of South Africa’s aloe species. It is “a primer”, says van Wyk, “showing aspects of their diversity, classification, evolutionary relationships, morphology, anatomy, physiology, ecology, biogeography, and significance to humans, especially in horticulture and medicine.” Both authors are taxonomists, inclined, says Smith “to collect ‘things’, and to classify, identify, and name them.” Not just animals, but plants, too, have complex behavioural patterns, rarely reflected in popular books, adds van Wyk, “and there is more to plants than just scientific names.” The challenge was to keep the text accurate, yet interesting enough for a lay audience. “Scientists tend to write dry texts,” observes Smith, and van Wyk concurs: “Scientists need to share their work and findings with society. So many fields of study have the status of ivory tower science. Popular scientific style promotes simplicity and clarity of thought. Jan Smuts once wrote: ‘All great truths are in their essence simple; and the absence of simplicity of statement only shows that the ultimate form has not yet been reached.’” Smith’s splendid photography is another highlight. “A picture speaks 1 000 words,” he comments, “and the bold and colourful shapes of aloes, especially when in flower, make it easy to create visual impact.” These plants are part of our natural heritage, adds Van Wyk, and should not be taken for granted: “Southern Africa has the richest succulent flora in the world: we should be proud of it, and active in enjoying, promoting, and protecting it.”
track number on the CD. “Simply follow the call and look for the bird that’s making it”, suggests the introduction. What could be easier? In between bird-watching, anyone walking in any part of the country will find it rewarding to watch out for butterflies, as South Africa has more than 660 species, and even small gardens in town provide a species list of a dozen or more. What’s that Butterfly? is an excellent and sensible introduction for the novice, clustering local butterflies into fewer than 60 groups for easy reference – complete with full-colour photographs and illustrations – and simplifying the information in a way that makes it less daunting for first-time learners. For specialist details, the author recommends consulting a comprehensive guide. But this book provides an attractive and excellent starting point. The Wildlife of Southern Africa: A Field Guide to the Animals and Plants of the Region. Edited (fully revised) by Vincent Carruthers. (Struik, 2008). ISBN 978 1 77007 704 1 Tortoises, Terrapins & Turtles of Africa. By Bill Branch. (Struik, 2008). ISBN 978 1 77007 463 7 A Guide to the Reptiles of Southern Africa. By Graham Alexander and Johan Marais. (Struik, 2007). ISBN 978 1 77007 386 9 A Guide to Animal Diseases in South Africa: Horses, Donkeys and Mules. By Pamela Oberem. (Briza, 2007). ISBN 978 1 875093 65 6 The Wildlife of Southern Africa first appeared in 1997 and this fully revised edition offers an updated, systematic overview of the natural
diversity in each of nine broad distribution regions in this part of the continent, focusing on those aspects of wildlife that aid identification. This is a compact book that tries nonetheless to be as comprehensive as possible – hence the use of abbreviations and small typeface. It can be used anywhere in southern Africa to find out more about a wide range of encounters – with lower invertebrates; spiders and other arachnids; insects; freshwater fishes; frogs; reptiles; birds; mammals; grasses; sedges; ferns and fungi; wild flowers; and trees. The illustration and text combination makes this genuinely the single book it’s worth having in case you meet something – of any kind! – about which you’d like more information as you explore this part of the world. For getting down to specifics, you’ll want books with the depth that an overview can’t offer. Tortoises, Terrapins & Turtles of Africa is one of the few popular publications that introduce these reptiles to interested naturalists, and it’s particularly useful since South Africa is home to the world’s richest diversity of tortoises.
Q Books Proxima: The Nearest Star (other than the Sun!). By I.S. Glass. (Mons Mensa, 2008). ISBN 978 0 9814126 0 3 South Africa’s unique astronomical distinction is to have achieved, in 1833, the first ever measurement of the distance to a star (Alpha Centauri – thought then to be our nearest neighbour), and subsequently, the discovery in 1917 of Proxima, the nearest one we know1. “These measurements are undoubtedly among the most revolutionary and significant contributions of the South African observatories”, explains Ian Glass. The research into Thomas Henderson’s work on Alpha Centauri has remained relatively unknown to the public, while the circumstances of Robert Innes’s discovery of Proxima have not been examined until now. Glass is concerned that South Africans are not familiar enough with the country’s history of science and engineering. “We do not have a serious national science museum and the ‘Exploratorium’ institutions do not fill the gap, as they are orientated too much towards children … a museum covering science, engineering, perhaps transportation, and inventions could have public appeal and is worth state support. Many people would be interested to know more about, for example, the South African atomic bomb project, the Pebble-bed Modular Reactor, and future installations such as the Square Kilometre Array.” This clear, interesting, and accessibly-written book explains how the orbit of the earth in Copernicus’s Sun-centred Solar System provides a
The volume covers sub-Saharan Africa and its coastal islands, including the 46 species of chelonians found here. Assisted by the excellent photographs, it shows a reader how to identify different varieties and where they might be found. And it offers informed advice about all manner of basic things – warning those who meet tortoises on the road, for instance, not to kill them with kindness by taking them home, but rather to release them immediately in the veld nearby, where they belong. It also summarizes the lives and conservation status of these shelled reptiles simply and clearly, in a way that makes them accessible to any curious visitor who wants to know more. For a broader view, a reader can turn to A Guide to the Reptiles of Southern Africa. It includes a section on tortoises, terrapins, and turtles, but also covers snakes of various kinds, lizards, and crocodiles. The reptile wealth of southern Africa is richer than that of the entire USA, the authors point out, yet it remains “a largely unappreciated and undervalued part of southern Africa’s natural heritage”, neglected by most conservation plans, and generally ignored in the region’s conservation management. At the time of going to press, there was a total of 517 described species for the sub-region (151 snakes, 338 lizards, 27 tortoises, and 1 crocodile), and new species descriptions are proceeding at an unprecedented rate. This volume provides an excellent overview, with illustrations and boxes full of interesting facts to accompany concise yet informative descriptions. It’s a must if you want to find – and find out about – this remarkable fauna.
natural baseline for finding the distance to the stars by trigonometry, and why the actual measurement proved so difficult. Although Henderson made the first valid observations of Alpha Centauri, he lost priority in publication, so Glass has described the work and successes of his rivals, 19th-century progress in investigating Alpha Centauri (the nearest and best-understood double star), and the 20th-century discovery of Proxima, here covered for the first time on the basis of the surviving correspondence. It took years of further work by astronomers to settle the question settled as to whether Proxima really was nearest. Glass has tried, as he says, to convey not just the science but the personalities of the main players. “Too often scientists are portrayed as rather flat characters, and I have shown that their undoubted talents are often accompanied by quite normal human failings!” Through this book, he also hopes to “stimulate further interest in the South African contribution to scientific knowledge.” 1. Read the article by Ian Glass, “Finding the nearest star”, in Quest, vol. 2, no. 2 (pp. 36–37).
On the animal-owner front comes another handbook – A Guide to Animal Diseases in South Africa: Horses, Donkeys and Mules. Its author, Pamela Oberem, has produced the first comprehensive veterinary guide for these animals to be published in South Africa. In a down-to-earth, practical way, it takes the user through all that he or she might need to know about the major diseases, parasites, physical problems, and sources of poisoning that affect these animals, with advice about how to look after them, and what treatment and prevention are recommended. The illustrations are large and clear, the style is readable, the range of facts and advice is invaluable for new owners – and even experienced ones – especially for people for whom their animals are important and who might not have immediate or easy access to information.
adjusted carefully for body type and the stage in the woman’s life. As a result, this book combines training information, with excellent illustrations and analysis of female-specific exercises, and detailed guidance through each of them. Text and visuals interact to clarify instructions, not only in terms of what needs to be done but also showing how the muscles and joints are working. The introduction explains the anatomical basics, and clarifies the kind of selfassessment needed as the basis for choosing and developing a personal programme. The core of the book is the exercise section, covering, in turn, aerobic training, postural stabilization and balance, chest, legs and hips, back and shoulders, arms, and stretches and flexibility. The author is rigorous and sensible – explaining the techniques for developing strength and fitness, but with understanding for the psychology of people starting out. He acknowledges, for instance, that there are resistance and transition phases before exercise turns from chore to lifestyle! The exercises are described in full, with analysis of the various movements as well as notes on possible injury risks, benefits, and ‘do’ and ‘don’t’ training details. This book is a first-rate way into exercise training, useful for personal trainers and exercise teachers as well as for women who just want to get the best out of their exercise routines.
Anatomy for Strength and Fitness Training for Women. By Mark Vella. (New Holland, 2008). ISBN 978 1 84537 952 0 This ‘how to’ book is written for women wanting to know how to exercise and build up their strength and fitness. Research during the past decade has made it increasingly clear that a woman’s body needs different exercise from that of a man. Furthermore, adds the author, a woman’s exercise programme needs to be
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Diary of events Q Shows, talks, & courses ■ Iziko Planetarium, Cape Town For young children – “Sunshine Simon and the dark day” 27 Sept–5 Oct: Mon–Fri at 12:00 & 13:00; Sat & Sun at 12:00. The “Twinkle Show” Until 24 Sept: Sat, Sun, & 24 Sept at noon. For teenagers & adults – “The Sky Tonight” Lecture on the current night sky every Sat & Sun, & 24 Sept at 13:00. “Do the stars influence your life?” Mon–Fri at 14:00; Tues at 20:00 (& sky talk); Sat, Sun & 24 Sept at 14:30. For information call (021) 481 3900 or visit www.iziko.org.za.
■ SciBono Discovery Centre, Newtown, Johannesburg 25–29 Aug ICTE (Information, Communications, Technology and Electronics) Careers Week For IT training and study opportunities. 8–12 Sept Youth in Construction Week Expo, talks, and workshops for learners interested in the construction industry. 15–19 Sept Finance Careers Week Exhibition covering the field of finance. Aug–Nov IT Clubhouse Learners create their own animations, devise computer-generated music, develop websites and many other things. Mon–Fri 14:30–16:30; Sat 09:00–15:00. Entry: free. For information call (011) 639 8400 or visit www.sci-bono.co.za. ■ Botanical Society of South Africa (Bankenveld Branch), Walter Sisulu National Botanical Garden (WSNBG), Gauteng For bookings phone Karen at (011) 958 0529 (mornings) or e-mail firstname.lastname@example.org. 6 Sept (09:00) “Spring trees in the garden” Identification Walk with Walter Barker. Main entrance (WSNBG). 13 Sept (09:00) “Gardening with indigenous trees” Talk by Suzette Vlok. Nestlé Environmental Education Centre (WSNBG). 20 Sept (09:00) “South African rock art” Talk by Ben Smith. Nestlé Environmental Education Centre. 27 Sept (06:30) “Spring bird identification walk” With Ella Jansen van Vuuren. Main entrance (WSNBG). 4 Oct (09:00) “Snakes” Slide show by Gavin Wilson. Nestlé Environmental Education Centre. 11 Oct (09:00) “Scorpions” Talk & walk with Jonathan Leeming. Nestlé Environmental Education Centre. 18 Oct (08:30) “Melville Koppies spring
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flower walk” With Wendy Carstens and Peter Johnson. Marks Park parking area. 1 Nov (18:00) “Fun frog walk” Family outing with Andrew Hankey. Main entrance (WSNBG). 15 Nov (09:00) “Butterflies” Talk by Herman Staude. Nestlé Environmental Education Centre. 13-17 Oct Marine week outreach With Bayworld Museum and SAIAB for Grades 4–12 learners at Wilderness National Park, Knysna National Park, and Tsitsikama National Park. Visit www.bayworld.co.za. ■ Spider Club, Gauteng 27–30 Sept Yebbo gogga Oppenheimer Life Sciences Building, University of the Witwatersrand, daily 10:00–16:30. Entry: free. 25 Oct Beginners’ identification course Sandton Field and Study Centre. To book, phone Astri (011) 958 0695 or e-mail email@example.com. 8 Nov Marievale Bird Sancturay Outing with Steve Langton. To book, phone (011) 818 1402 or e-mail firstname.lastname@example.org. ■ Mid-Sept–end Oct DAAD Johannesburg research lecture series on energy science, environmental sciences, and neurosciences. Visit www.ic.daad.de/ johannesburg/events. ■ Radio astronomy at HartRAO (group visits by arrangement). Call (012) 326 0742/6/7; fax (012) 326 0756; e-mail email@example.com; visit www.hartrao.ac.za.
Conferences & exhibitions 15–17 Sept “INSITE 2008” DST’s biennial Premier Science Exhibition, running concurrently with the International Association of Science Parks’ XXV World Conference on Science and Technology Parks (e-mail firstname.lastname@example.org); and the Bio2Biz Conference (e-mail email@example.com). 6–9 Oct “A quarter of a century of research on HIV/AIDS: Lessons and challenges” at the Hotel du Golf (Côte d’Ivoire Abidjan). Visit www.csrs.ch/cissida08. 23–26 Nov SAASTEC conference “Developing scarce SET skills – how science centres can make a difference” at the Sci-Bono Discovery Centre, Newtown, Johannesburg. Visit www.saastec.co.za or e-mail Ginny Stone at firstname.lastname@example.org.
Note and diarize ■ Visit www.biodiversityexplorer.org for the Iziko Museums of Cape Town’s biodiversity explorer website and information about spiders, scorpions, birds, mammals, plants and other things ■ Support the Jane Goodall Institute SA Adopt-a-Chimp Programme. Visit www.janegoodall.co.za/adoptachimp.asp ■ Subscribe to CSIR eNews by visiting http://ntww1.csir.co.za ■ August Marine Biosciences month September African Origins month October Astronomy month ■ 1 Sept Deadline for SAB Environmentalist and Environmental Journalist of the Year award entries. Visit www.sabenvironment.co.za ■ 25–31 March 2009 SciFest Africa, Grahamstown Visit www.scifest.org.za
AfricA South AfricA for South Sciencee for Scienc
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The first four years
uring its early years, a magazine – like any newborn – needs special care and nurturing if it’s to survive. QUEST owes its continued existence to many people who have given it life in different, yet crucial ways: the Department of Science and Technology has supported it from the start, and without all our authors, editorial advisers, and readers, it could never have progressed beyond its initial launch. Not to be forgotten are special individuals who worked hard behind the scenes: Graham Baker (of the South African Journal of Science) who conceived the idea in the first place, designed the model, and acted as guide; Wieland Gevers (as President of ASSAf), who saw the potential and ran with it; Hennie Smith (then Administrator of ASSAf), who set up the logistics; Neville Pritchard, who established the infrastructure; and the team who have made it all happen and kept us going – designer Ria Rademeyer Buckley (Creating Ripples), May Chellew, Eldaleen Hugo and Lizel Kleingbiel, Meg and Alan Kemp, Liesel Smith, Barbara and Ryan Spence (Avenue Advertising), the staff at Paradigm Print and Prestige Bulk Mailers, and all our supporters at ASSAf. And now, welcome to Bridget Farham, the magazine’s new editor. – Elisabeth Lickindorf (outgoing editor)
Q ASSAf News
Water-powered energy In June 2008, in Pretoria, ASSAf and the Water Research Commission hosted an African Hydrology and Hydropower training workshop to investigate the use of hydropower in Africa. Hydropower is a renewable energy source, involving large-scale projects as well as small-scale hydro schemes that serve small communities. Africa has used less than 10% of its hydropower potential, and the workshop examined ways to harness this method of generating sustainable and reliable power on the continent1. The large projects are often implemented in downstream countries, so as to use to best effect high rainfall patterns and other favourable hydrological conditions upstream. Most such projects are connected to regional power grids that supply several nations. Successful
implementation creates a setting for increased economic growth, employment creation, poverty alleviation, and better quality of life for all – but environmental and social impacts need careful management. For workshop details and full report, contact Simon Rambau (ASSAf) at email@example.com or Renias Dube (WRC) at firstname.lastname@example.org.
People on the move Professor Wieland Gevers has retired as ASSAf’s first Executive Officer (but continues working on ASSAf committees). He is succeeded by Professor Roseanne Diab (University of KwaZulu-Natal), an atmospheric
scientist with broad interests in the environmental sciences and research at the interface of the natural and social sciences. South African-born Professor Sydney Brenner has been nominated as the ASSAf’s first honorary foreign associate2. Two woman scientists from the University of Cape Town, Zenda Woodman and Sheen Mowla, are the current post-doctoral recipients of the Sydney Brenner Fellowships3, initiated by his donation of part of his 2002 Nobel Prize, and co-awarded by ASSAf and the US National Academy of Sciences with additional funding from the Oppenheimer Memorial Trust3.
1. Topics covered in the workshop included regional hydrology; climate change and energy security; established hydropower schemes (large, medium, and small); potential new schemes in Africa; environmental impacts and mitigation; social impacts and mitigation; biodiversity and threatened species; hydropower infrastructure and integrated water resource management; case studies and examples in emerging economies; partnerships in regional hydrology; and financing hydropower schemes. 2. Read about Sydney Brenner’s achievements in Keith Manchester’s article, “Sydney Brenner: a most distinguished biologist”, Quest, vol. 1, no. 3 (pp. 22–23). 3. For more on the Sydney Brenner Fellowships, see Quest, vol. 2, no. 3 (p. 47).
Public statement on the importance of teaching evolution in South African schools The Academy recognizes and appreciates the fact that the teaching of evolution in schools is a sensitive matter in certain segments of society, especially in some religious communities of South Africa. At the same time, one of the beneficial outcomes of the democratic transformation of the country since 1994, and especially of the adoption of the Constitution and the Bill of Rights, is an openness to knowledge that is widely accepted and usefully applied for society’s benefit by the scientific community, and that is fundamentally important for meeting our developmental challenges. The Academy takes the position that it is unwise and inappropriate for any group of citizens, religious or otherwise, to limit access of any young people to the means to understand the workings of the natural world, and especially to deprive them of the knowledge which would enable them to become properly equipped practitioners of professions and occupations dependent on such concepts and understanding. They also need to use this understanding for democratic participation in national policy debates, and to make their own judgements on substantive issues that impact upon their lives. Fully understanding the nature of evolutionary processes and mechanisms is fundamental to functioning in the modern world; without it, for example, the practical implications of the progression of HIV infections in affected persons cannot be understood, nor the incidence of, and variable susceptibility of people and populations to many other diseases. Without an understanding of how and why otherwise closely related plants and animals are different from each other, one simply cannot deal with hugely important matters such as our security with respect to staple foods, environmental sustainability for both animals and plants, emerging threats of pandemic infections caused by organisms normally resident in domestic or wild animals, and many other matters affecting life and society. Not having a proper grasp of evolution is like trying to understand and use physics without Newton’s laws of motion or the various laws of gases, or to practise chemistry without a full
understanding of molecules and chemical bonding. Evolution is fundamental to biology, based as it is on the centrality of cells as basic structural units of organisms, and biology is one of the key fields of knowledge about our world. The two go hand in hand: you cannot have one without the other. Our knowledge of evolution derives from a mode of enquiry into the nature of living things that has been enormously successful and of great significance to every citizen. This enquiry focuses on observing the natural world, and formulating testable and refutable hypotheses to derive deeper explanations for observable phenomena. When evidence is sufficiently compelling, conceptual syntheses can be developed that explain that evidence, and predict the likely structure or process of still unobserved phenomena. Much progress is made when unifying conceptual advances are made; evolution through natural selection is one of the most significant of such advances in the entire history of our search to understand the natural world. No learner should be deprived of its enormous explanatory potential, power and beauty. Depriving learners of an educational grounding in evolutionary concepts is a serious limitation of their opportunities and rights. In turn, providing a conceptual grounding in evolution is not a limitation on religious freedom, as countless active biologists are deeply religious, in many faiths. In making this public statement, the Academy is acutely aware of the importance that South Africa’s diverse citizenry attaches to matters of religion, faith, and belief. A number of elements – social, philosophical, religious, cultural, and political – contribute to human consciousness, motivation, and behaviour, in individuals and in groups. The fields and disciplines that study these elements in detail (most of them well represented in our Academy) owe each other mutual respect and consideration, while maintaining their own integrity and modes of enquiry, including their ways of seeing the world and society. – The Academy of Science of South Africa
Quest 4(3) 2008 55
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56 Quest 4(3) 2008
Q Back page science Thoughts for the day ■ “Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information?” – T.S. Eliot (1888–1965), poet. ■ “Books are the compasses and telescopes and sextants and charts which others have prepared to help us navigate the dangerous seas of human life.” – Jesse Lee Bennett (1907–2000), author. ■ “Nothing produces such odd results as trying to get even!” – Franklin P. Jones (1887–1929), businessman.
Beady eyes on the first meal Cuttlefish develop a taste for either crabs or shrimps depending on what they see from inside their translucent eggs while they are embryos. Research at the University of Caen in France provides the first proof of any unborn animal being able to learn from what they see. Other research has shown evidence of embryos learning scents and sounds. Reported on www.sciencenews.org, 2 July 2008.
The milkweed case The relationships between species can be difficult to untangle. A study of milkweed plants and the aphids and ants the plants host suggests why. The aphids feed on the milkweed sap and secrete a fluid, which the ants feed on. The ants keep predators off the plant. Researchers planted genetically distinct groups of milkweed and looked at what happened to the insects on them. On some of the plants, the presence of ants increased the aphid population; on others, ants had the opposite effect. More insects give the plant more protection from caterpillars but at the cost of sap being sucked out. Different situations suit different plant genotypes best, and this creates a more complex picture for the milkweed species as a whole. Reported in Science Now, http://sciencenow.sciencemag.org, 24 June 2008.
Weather veins The way the veins are arranged on a leaf is governed by a mathematical principle that ensures optimum plant growth. When plants open their pores to take in carbon dioxide during photosynthesis, they also lose water, so they need to pull more water up from their roots and distribute it before they dry out. Harvard scientists have shown that there’s a formula for the best vein
pattern to get water moving to where it’s needed fast. A particular pattern evolves for each species. This may also shed light on climates long ago, by making it possible to calculate the availability of rainfall and sunshine from fossil leaf vein patterns. Another potential application of this insight is in the design of irrigation systems. Reported on www.sciencenews.org, 30 June 2008.
Flashy old bird Fossils yield more and more information as science advances. Now US researchers have a new interpretation of light and dark bands on certain 100-million-year-old fossil feathers. The dark bands had a grainy texture under the microscope, previously thought to be fossilised bacteria. But the dark feathers of modern birds have the same microscopic structure, consisting of melanosomes. The arrangement of melanosomes corresponds to certain colours, leading the researchers to believe that they may be able to tell the colours – and even the iridescence – of fossil feathers. That, in turn, could reveal information about behaviour such as courtship displays. Reported on http://news.bbc.co.uk, 8 July 2008.
Under granny’s wing For the first time, ‘grandparent’ behaviour has been observed in birds. Research over 20 years on Seychelles warblers has shown that older, nonbreeding adults often assist their offspring in raising their young. Helpful subordinate adults have been observed in birds, mammals, and some fish before, but they have normally been older siblings of the young being raised. The warbler grandparents appear to have taken on this role because there is not enough habitat available for them to breed. Reported on www.sciencedaily.com.
Learn by doing “There has been much debate among scientists about whether communities of chimpanzees copy behaviour from each other or work out how to carry out tasks themselves,” according to the Royal Society, London. Human children seem to be good imitators, learning by copying others’ actions. Researchers compared how four-year-old children and adult chimps learnt to slide a door sideways to reach a reward. Though the apes could learn from observing simply the
results of actions – in this case, what happened when the door slid automatically, without chimp intervention – they depended more on role models than children did. Reported on http://royalsociety.org/news.
The neck knows You’re looking, but are you paying attention? A Canadian scientist, Brian Corneil, has found a way to measure attention by recording muscle activity in the neck. This could help to assess the effectiveness of therapies for stroke and Parkinson’s disease. Reported on www.sciencedaily.com.
An idea whose time has come What makes one idea catch on and another fail? Social network theorists Duncan J. Watts of Columbia University and Peter Sheridan Dodds of the University of Vermont in the USA ran some tests. They found that people didn’t necessarily accept and spread an idea just because their friends or an influential person supported it. The study concluded, said Dodds, that “in the end, you don’t have control over how people spread your message.” The best way to increase the odds of person-to-person transmission of an idea is for it to be a good idea with “social worth”, he explained. “Some things are just fun to talk about.” We knew that. Reported on www.sciencenews.org. 5 January 2008.
Bank of stories The wisdom and humour of great thinkers and achievers is being stored for public access in a website called People’s Archive. There, you can see a video of these people telling their stories, or read a transcript of the interview. In the science category, some achievers featured so far are Francis Crick, Sydney Brenner, Benoit Mandelbrot, and Freeman Dyson. Visit http://peoplesarchive.com. Answers to Crossword (page 51) ACROSS: 2 Dormant, 4 Extinct, 5 Health, 6 Debris, 8 Pandemic, 10 Moon, 13 Charcoal, 14 Elytra, 18 Uranium, 19 Diabetes, 23 THUSA, 24 Haem, 25 Pupa, 26 Anaemia. DOWN: 1 Fibrin, 3 Nutrient, 4 Endemic, 7 Bacillus, 9 Explant, 11 Iron, 12 Thaw, 15 Addo, 16 Labour, 17 Nectar, 20 Lemon, 21 Bana, 22 Lava.
MIND-BOGGLING MATHS PUZZLE FOR Q UEST READERS Q UEST Maths Puzzle no. 7 An arithmetic expression is formed using digits 1, 2, 3, and 4 (each may be used only once in an expression) and the operators addition (+), subtraction (–), and multiplication (x). Operators can be used more than once and digits can’t be joined (for example, 123 is not permitted). In such arithmetic expression, 1 can be represented as [(2 × 3) – (1 + 4)], 2 can be represented as [(2 × 3) – (1 × 4)], 10 can be represented as [1 + 2 + 3 + 4], etc. What is the smallest positive integer that cannot be represented by such arithmetic expressions?
Win a prize! Send us your answer (fax, e-mail, or snail-mail), together with your name and contact details, by 15:00 on Friday 17 October 2008. The first correct entry that we open will be the lucky winner. We’ll send you a cool Truly Scientific calculator! Mark your answer “QUEST Maths Puzzle no. 7” and send it to: QUEST Maths Puzzle, Living Maths, P.O. Box 478, Green Point 8051. Fax: 0866 710 953. E-mail: email@example.com. For more on Living Maths, phone (083) 308 3883 and visit www.livingmaths.com. The winner of Puzzle no. 6 was Herman Kok (from Kroonstad).
Solution to Q UEST Maths Puzzle no. 6 Let the sides of the right-angled triangle be a, b, and c, with c = 240 being the hypotenuse. The triangle has the minimal circumference when a = 1 and b = √ (c2 – 12) (approximately 240.0). The circumference in that case is approximately 480.0. The triangle has the maximal circumference when a and b are equal: a = b = √ (1/2 × c2) (approximately 169.7). The circumference in that case is approximately 579.4. The only two squares of whole numbers that lie in the interval [480.0, 579.4] are 529 and 576. Now we know that a + b = 529 or a + b = 576. In addition, a2 + b2 = c2, so a2 + b2 = 57 600. Suppose that a + b = 529. Then b = 529 – a, and when we substitute in a2 + b2 = 57 600, we get a2 + (529 – a)2 = 57 600, so a2 – 289 × a + 12 960.5 = 0. This equation has no solutions if a must be an integer. Suppose that a + b = 576. Then b = 576 – a, and when we substitute in a2 + b2 = 57 600, we get a2 + (576 – a)2 = 57 600, so a2 – 336 × a + 27 648 = 0. This equation has solutions a = 192 (b = 144) and a = 144 (b = 192). Therefore, the sides of the triangle are a = 144, b = 192 (or vice versa), and c = 240.
Quest 4(3) 2008 57
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