Polynesia is probably the best region in the world to understand the origin and dispersal of human groups and its impact on naïve environments, as Professor David Penny, Institute of Molecular BioSciences, Massey University, explains: When Captain Cook and his naturalists first sailed around the South Pacific they wondered how the distant and remote islands of Polynesia were settled. Where had the people come from? How had they got to these islands? The Europeans considered themselves great sailors and navigators (and they were), but they recognised it would have taken another people with great sailing and navigation skills to have discovered and settled Polynesia (Figure 1). In their talking with Polynesian navigators they were quickly convinced from the knowledge of the Polynesians that they knew a lot about navigation at sea – the stars and constellations, waves, and how the behavior of sea birds could be used to indicate the direction of land. So really, there were two great sets of sailors and navigators in the Pacific: the Polynesians and the Western Europeans. What does modern science tell us about where the Polynesians came from? What extra will it tell us in the future? We do need to be careful – we will get different answers at different times, for example, where were the Polynesian ancestors 2000 years ago, 3000 years ago, 4000 years ago, etc. Because it occurred so recently, Polynesia is probably the best region in the world to understand the origin and dispersal of human groups, their domesticated plants and animals, cultural and linguistic evolution, and human impacts on a pristine environment.
A brief background to the region 14
C dating indicates that modern humans entered Australia and New Guinea by ~50 000 BP (before present) – soon after the DNA evidence shows modern humans spreading out from Africa. Although Australia and New Guinea were connected during periods of lowered sea levels, the first settlers must still have crossed the open ocean from Southeast Asia. By 29 000 BP, people had colonized the Bismarck and Solomon Islands, which together with New Guinea, form ‘Near Oceania’. But nobody was in Polynesia. Then, around 3300–3500 BP, a new culture – Lapita – appears in the archaeological record of Near Oceania, and in a previously unoccupied coastal niche (their stilt houses were often built over beach reefs or shallow lagoons). Lapita is characteristically defined by a decorated pottery style, and is named after an excavation site in New Caledonia. Lapita culture introduced new features, including permanent villages, a range of horticultural crops, domesticated animals (pigs, dogs, chickens and rats), fishhooks for inshore and open ocean fishing, fishing nets, seagoing canoes, stone adzes, anvils and shell bracelets. Although this expansion is thought to have started in China following the domestication of rice, it may have been in Taiwan (5000–4500 BP) that the basic canoe building expanded, and we can trace the expansion back that far. From Taiwan the expansion continued to the Philippines (4500–4000 BP), to Wallacea (the biogeographical area
NZ
between Borneo and New Guinea, Figure 1) and to Near Oceania. Within another 200–300 years the Lapita culture is found in some parts of previously uninhabited ‘Remote Oceania’ (Eastern Melanesia, Micronesia, and Polynesia – including sites in Vanuatu, New Caledonia, Fiji, Tonga and Samoa). Then there appears to be a pause of at least 1000 years before permanent settlement of the easternmost islands of Polynesia; greater skills in sailing and navigation were required. So Taiwan is the start of our answer.
What does molecular genetics tell us? The two main markers used so far are the mitochondrial DNA (mtDNA, which is inherited maternally by both sons and daughters) and the Y-chromosome (inherited paternally, but in males only). An important ‘signature’ in most Polynesian mtDNA is the loss of one copy of the sequence CCCCCTCTA of some individuals. In other words, most humans have two copies repeated one after the other (CCCCCTCTACCCCCTCTA), but because it is in a ’spacer’ region between two genes it doesn’t seem to matter whether one, or two, copies are present. Thus the mutation is thought to be ‘neutral’; ‘neither beneficial nor injurious’ in Charles Darwin’s words. We summarise this as a 9-bp (base pair) deletion, and the loss seems to have happened occasionally and independently in different parts of the world. Together with three other mutations the 9-bp deletion forms a ‘Polynesian Motif,’ and its distribution is very informative. The full motif has its highest frequencies in Polynesia (where it predominates), and is largely confined to speakers of the Central/Eastern Malayo-Polynesian subgroup of Austronesian languages in Wallacea and the Pacific (Figure 1). Stepping backwards, the ancestral lineage with two out of the three mutations (plus the 9-bp deletion) is found across the range of Austronesian speakers from Madagascar to Easter Island. However, the earlier lineage (with only one of the three mutations) is confined to the central part of this range, and among the indigenous Formosans. Thus, this pattern of a directional series of mutations shows the dispersal of the 9-bp deletion from Taiwan. Earlier still it must have come from somewhere in East Asia, but there have been too many population changes there to follow it yet. Basically, the mtDNA and the archeology agree about Taiwan.
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futurefocus–DNAandpolynesianmigration
Taiwan and the origin of Polynesians
science teacher
What can we learn from languages? Before moving to the Y-chromosome, let’s consider languages. It may seem surprising, but we can use similar methods for analyzing the evolution of languages as for the evolution of DNA seqeunces. Austronesian (including Polynesian) is the world’s largest and the most widely distributed family of languages. Its ~1200 languages are classified into ten subfamilies, nine of which are spoken only by indigenous Taiwanese (the Formosans). By contrast, languages of the tenth subfamily, Malayo-Polynesian, are spoken from Madagascar (47° east) to Easter Island (109° west), and their relative similarity suggest that they share a recent common origin. Examine the words in the different languages in Figure 2. The world waka, vaka, va’a and wa’a is considered the same word; the ‘v’ ‘w’ change is quite common between related New Zealand Association of Science Educators
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