FAQs for biological anthropology
Many students take a course in biological anthropology without much background in science. As a result, they have a lot of questions. So, we’ll start this book by introducing a bit of scientific context and history. This information, along with the illustrations in this section, will be useful to set the stage for the rest of the book. How Old Is the Planet and What
Organisms Have Lived on It over That Time?
Before we begin discussion about human biological evolution, we need to review the evolution of the planet and life on it. Let’s quickly run through the last 4.5 billion years of the planet’s geological and biological history to give us a little perspective on the relative context of humankind. The history of this planet is divided into eras, which are divided into periods, which are further divided into epochs (Figure I.1). The majority of the earth’s history is in the Proterozoic era. The Proterozoic began with the formation of the earth, approximately 4.5 billion years ago, and ended with the first major diversification of life-
forms, approximately 600 million years ago. It is in this era that we find the first hints of life on this planet: tiny fossilized impressions suggesting clusters or chains of linked cells resembling today’s blue-green algae and bacteria (prokaryotic cells, or cells that do not contain a nucleus). From about 3.5 to 1.5 billion years ago, these are the only kinds of fossils we find. So, prokaryotes were the only organisms on the planet for the first 2 billion years of the evolution of life. ■ FIGURE I.1
The geological timescale shows the sequence of appearance of the major forms of life on earth. Starting around 1.2–1.5 billion years ago, lifeforms became slightly more diverse. We begin to find evidence of eukaryotic cells (cells that have a nucleus, like those of all animals and plants). By 1 billion years ago, we find indirect evidence (fossilized burrowing tracks and fecal pellets) of multicellular organisms. Between 1 billion and 570 million years ago, we see a diversification of types of fossil organisms; however, all life is still very small and confined to limited habitats in the
oceans. 3 The next geologic era, the Paleozoic, began around 540 million years ago. The first period of the Paleozoic era, the Cambrian, shows the first major example of an adaptive radiation (expansion by a single group of organisms into a diverse array of forms) that we see in the fossil record. At the start of this period there was an explosion of forms moving into a wide array of new niches, or habitats and lifeways, in the oceans. From the basic structures of organisms in the late Precambrian, we see a multitude of variants arise as organisms exploit new oceanic environments and ways of making a living. By the end of the Cambrian period, we have the first precursors for many modern animal lineages. adaptive radiation expansion by a single group of organisms into a diverse array of forms 4 Throughout the rest of the Paleozoic we see an array of new forms arising from existing varieties. In the Ordovician we see a great expansion in complex multicellular organisms, including the first fishes (jawless fishes). By the beginning of the Silurian we find
fossils of jawed fishes, which suggests a radical change in the cycle of life (that is, the appearance of active chewing). These are the first serious vertebrate predators. These earliest jawed fish have no bones, only cartilage, and at least one lineage of these early Silurian fish is ancestral to modern sharks and rays. By the middle of the Silurian, bony fish show up in the fossil record and diversify into at least two main groups: the lobefinned and the ray-finned fishes. The currently favored hypothesis is that one or more lineages of lobe-finned fishes gave rise to the first land vertebrates (the amphibians). The first fossils of land plants show up during this period. By the end of the Devonian, we have evidence of land animals (insects), complex land plant formations (like swamps), and a huge array of life-forms in the seas. From the rest of the Paleozoic we find a growing number of fossils of land animals, especially in coastal areas, where the early amphibians (which looked very much like slightly modified lobe-finned fish) gradually changed into
a wide array of amphibian forms and early reptiles. During the last period of the Paleozoic (the Permian), there was a broad radiation of reptilian forms, including a group called the therapsids, or mammal-like reptiles (the reptile group that mammals are hypothesized to be most closely related to). The Mesozoic era began around 250 million years ago. By the early Mesozoic, reptiles had undergone a broad and dramatic adaptive radiation. Freed from the water by two crucial adaptations—self-contained eggs and skin that resists drying out—reptiles spread across the land environments and adapted to a broad spectrum of habitats. During this era the best-known reptile group, the dinosaurs, make up a large portion of the fossil remains. It is also during the Mesozoic that the first mammals show up (Figure I.2). These mostly small, probably nocturnal, insect-eating mammals are found throughout the era, but do not make their grand adaptive radiation until the Cenozoic. ■ FIGURE
I.2 An artist’s conception of an early mammal
from 195 million years ago. The Mesozoic was the age of reptiles. The Cenozoic, which began around 65 million years ago, is the age of mammals and birds. After an enormous extinction event at the Mesozoic-Cenozoic boundary, mammals and birds began to diversify, filling many of the niches left vacant by the extinctions of reptiles and other types of animals. The Cenozoic period is very important in the history of primates (and therefore humans) and is covered in detail in chapter 6. 5 If Life on Our Planet Has Changed So Much Over Time, What About the Planet Itself? During the time that life on earth has been changing, so has the surface of the planet. The process of plate tectonics drives the phenomenon of continental drift. Plate tectonics results from the continental plates floating on a layer of mantle (magma, or molten rock, like lava) (Figure I.3). Currents in the magma move the plates in a number of different ways. Sometimes magma pushes up between plates and solidifies, pushing them apart (spreading). When plates
meet, one can overlap the other, driving it down into the magma (subduction). Plates can move against one another, pushing the earth up and creating mountain ranges (collision). If we look at the model of continental movement over just the last 200 million years, we can see that the earth’s surface has changed dramatically over time (Figure I.4). plate tectonics process by which the earth’s crustal plates move independently of one another, resulting in continental drift continental drift theory that the present configuration of continents results from the movement of the earth’s crust ■ FIGURE I.4 Continental drift. The continents took on their present relative positions only about 35 million years ago. The forces of plate tectonics continue to reshape the crust.
©Science Source ■ FIGURE I.3 Model of the earth’s interior, showing the layers. This demonstrates the earth’s crust “floating” on the liquid mantle. Understanding that the earth and life on it have changed over the last 4.5 billion years is an important basic concept. You will
notice throughout this book that change over time is a recurring notion in biological anthropology. Have Humans Changed? Yes, absolutely, humans have changed. Change over time in humans is pretty much the core of biological anthropology. So, thinking about change on a slightly smaller scale than 4.5 billion years, let’s turn to another basic set of information that we’ll be expanding upon throughout this book—the history of humans and their immediate ancestors over the last 6 million years or so. Figure I.5 is a simplified time line of human history over the last 6 million years. This time line is just a brief outline to get you to start thinking about names, places, and dates in human evolution. We’ll be discussing each of the names and types of human and humanlike organisms in detail in chapters 6 through 11. Notice, however, that during most of the time that our species has been evolving, more than one humanlike species existed side by side. While trends and patterns are evident in the history of human evolution, 6 there is not an
inevitable trajectory. Knowing this may help you realize that our species is just one of many on this planet that evolved by filling, modifying, and being modified by different niches. ■ FIGURE I.5 An evolutionary time line of human history. In this book we will explain what these different organisms are and how they might be related to us. Where Did Modern Science Come From? All of the information we’ve just reviewed and much of what we will be introducing in this book is the product of a process we call science. The methods and philosophy of what we call “science” today have deep roots but developed their modern form over the last 5 or 6 centuries and is largely what Francis Bacon called for in 1605: a collaboration 7 between inductive methodologies (drawing conclusions from extant facts) and experimental methodologies (testing hypotheses and making observations). This contrasts with the a priori methods wherein investigators go from cause to effect, basing their reasoning on beliefs or assumptions rather than
experience or testable observations. The hallmark of modern scientific knowledge is its falsifiability, not its verifiability; that is, science can prove things 100% false but not 100% true. To be falsifiable, statements must be capable of being subjected to tests that might result in their refutation. So scientific information emerges from series of observations, refutations, and hypotheses supported by rigorous testing. In this book we focus on scientific information and processes that relate to understanding our bodies and our biological history. It is important to realize that all our current knowledge rests on past discoveries and collaborations. For example, our understanding of the cells that make up our bodies has developed over 350 years. It began in 1665, when Robert Hooke first described cells. In 1683, Anton van Leeuwenhoek used his early microscopes to examine blood and sperm cells. In 1883, August Weismann recognized the role of gametes (germ-cells, or egg and sperm). In 1902, Emil Fischer proposed that proteins (the building
blocks of our cells) are made up of naturally occurring amino acids, and in 1926, J. Haldane described the complex internal structures of cells and their permeable membranes. All of these elements laid the groundwork for Erwin Chargaff’s 1950 discovery of the composition of DNA, for Rosalind Franklin’s images of DNA via X-ray crystallography, and finally James Watson and Francis Crick’s 1953 model of the structure of DNA. Similarly, our understandings of the basic patterns in our solar system and galaxy started with Johannes Kepler’s and Galileo Galilei’s observations and proposals in the early 1600s. These in turn supported Nicolaus Copernicus’s notions about the motion of planets and the sun as the center of the solar system. By 1704, Isaac Newton had published accounts of his ideas on gravity, optics, and particulate light; and approximately 200 years later, Albert Einstein began publishing his ideas about the energy source of the sun and the relationships among matter, mass, and light. In 1929, Edwin Hubble
published his observations that all galaxies were moving away from each other. Today all of their proposals, plus many others, are integrated in our understanding of the motion of the earth and all other celestial bodies.
Introduction to Evolutionary Fact and Theory
This chapter addresses these questions: What is anthropology, and what areas does it cover? What is the scientific method, and how does it work? How is evolution a fact and a theory? Where do our ideas about evolution come from? Why is the theory of evolution important, and why is it so misunderstood? n 1925 the theory of evolution went on trial in the United States. A Tennessee court case the famous Scopes
“Monkey Trial”—was the arena for a debate about whether evolution could be taught in the public schools. The case had all the elements of high drama, including great speakers, impassioned
arguments, and a county courthouse packed with spectators and journalists in 100-degree heat (Figure 1.1). On trial was John T. Scopes, a 24year-old science teacher who admitted teaching evolution in the local high school, in violation of state law. The American Civil Liberties Union wanted to test the constitutionality of that law, and Scopes agreed to be their test case. ■ FIGURE 1.1 The Scopes trial. Clarence Darrow, the lead defense attorney, is leaning on the desk at the center of this photo; William Jennings Bryan is behind him (light jacket). The high-stakes nature of this trial is palpable. ©Pictorial Press Ltd/Alamy Stock Photo Tennessee, like many states of that time, had passed a law against teaching evolution—specifically, against teaching “any theory that denies the story of divine creation of man as taught in the bible”—because it was viewed as a threat to the American way of life. The theory of evolution was popularly, and wrongly, believed to suggest that humans were descended from monkeys, a notion considered both
ridiculous and blasphemous. The prosecuting attorney, William Jennings Bryan, even called the case “a contest between evolution and Christianity” and portrayed the defense lawyer, Clarence Darrow, as “the greatest atheist … in the United States.” Bryan had had a career in national politics, having served as secretary of state under Woodrow Wilson and having run for the presidency himself three times. In recent years he had joined the “tent revival” movement, touring the country as a fiery evangelical preacher. Darrow, the nation’s 15 most prominent defense attorney, wanted to challenge what he saw as provincial resistance to progress and scientific ideas. He also wanted to show that the theory of evolution did not inherently conflict with the teachings of Christianity. Darrow had several experts lined up to explain evolution and show how it was compatible with the Christian faith, but the judge would not allow him to put them on the stand. Undeterred, Darrow asked Bryan himself to take the stand. Darrow then asked Bryan a series
of questions aimed at exploring how a literal interpretation of the Bible could be reconciled with the laws of nature and with known facts about the earth and its peoples. Bryan started off gamely but soon became entangled in inconsistencies and absurdities; ultimately, he was revealed to be a man who had given little thought to any ideas that differed from what he had been taught as a child. The cause he represented was similarly tarnished. The trial ended with Scopes being convicted of breaking the law against teaching evolution and fined $100. The verdict was overturned a year later, but only on a technicality, so the law remained on the books. The Tennessee law was finally repealed in 1967, and in 1968 the U.S. Supreme Court declared such state laws unconstitutional. The Scopes trial was dramatized (and partly fictionalized) in the mid-1950s in the play Inherit the Wind, by Jerome Lawrence and Robert E. Lee. Since then, the play has been performed innumerable times in countries around the world
and has appeared as both a Hollywood film and a television movie. With the Scopes trial more than 90 years in the past, the theory of evolution—an extremely well supported theory accepted by virtually all scientists in every country of the world—now enjoys a secure place in public school curricula, right? Wrong! In 2000, Kansas revised its statewide science standards to exclude all mention of evolution or any matters relating to the age of the earth or the universe, and in 2005 the Kansas board of education rewrote the definition of science. By 2007, state courts had overturned the board of education’s revisions, and in 2013 Kansas adopted standards that inserted some evolution back into the classroom, but the battle continues in Kansas even today. In 2004, Ohio moved to label the discussion of evolution as only one theory among many in 16 explaining life on this planet. As of 2017, some states continue to revise their standards to include topics related to biological and geological change over time without mentioning the word
evolution. Still other states place disclaimer stickers on all science textbooks that deal with evolution, stating that evolution is a “controversial theory” presented by “some scientists,” while others have statements in their education guidelines that state teaching about biological evolution can “cause controversy.” A 2014 survey by the Pew Research Center revealed that 62% of adults say humans have evolved over time, 33% say this change is due solely to natural processes, and 25% think evolution is guided by a supreme being. So a slight majority do understand that life on earth is changing over time, but this still leaves 38% of the United States denying a central biological fact. And as of January 20, 2017, the United States has a vice president who does not accept the theory of evolution—not a good sign.
STOP & THINK Do you know what the laws on teaching evolution are in your home state? Did you get any coursework on evolution in elementary or high school? What is it about the theory of evolution that makes its detractors so
angry and uncomfortable? Does it claim that people are descended from apes or monkeys? Does it try to disprove the Bible or make it impossible for people to hold religious beliefs? Is there an irreconcilable conflict between evolutionary perspectives and religious views and values? As you will see in this chapter, the answer to these last three questions is no. Evolution is a core principal of the sciences and is at the heart of anthropology. It is also one of the most widely misunderstood sets of ideas in our culture today. This chapter will help you understand what the theory of evolution is how it emerged from the thinking of many scientists over time, and what skills and methods are required in order to understand and investigate scientific issues. But first, a brief overview of anthropology is in order. Anthropology is the study of human and nonhuman primates The word anthropology comes from two Greek roots: anthropos, meaning “human,” and logia, meaning “study”—thus, “the study of humans.” We can expand this definition
by looking at the mission statement of the American Anthropological Association. The society’s mission is to “advance anthropology as the discipline that studies humans and nonhuman primates in all their aspects, through archaeological, biological, ethnological and linguistic research, and to foster the use of anthropological knowledge in addressing human problems.” From this mission statement we can see, then, that anthropology is the study of humans (us) and our closest biological relatives (other members of the order Primates— monkeys, apes, and prosimians). anthropology the study of all aspects of the human experience Primates mammalian order to which humans belong Anthropology is often described as being divided into four traditional areas of investigation: archaeology, biological anthropology, cultural anthropology, and linguistic anthropology. In practice these areas overlap extensively, and the best anthropology emerges through collaboration across them. Anthropologists are committed to
ensuring that the knowledge they acquire is made available to nonanthropologists and is applied to issues facing humanity. What areas of study are included in anthropology? An archaeological anthropology involves the study of the material past of humans: what the people of the past made, how they lived, and how they modified their environment, as evidenced by the material clues they left behind. Biological anthropology (which used to be called physical anthropology) focuses on the biological facets of the human species, past and present, along with those of our closest relatives, the nonhuman primates (monkeys, apes, and prosimians). Cultural anthropology is the study of that extremely complex entity we call human culture: the patterns of behavior we exhibit in our families, relationships, religions, laws, moral codes, songs, art, business, and everyday interactions. The main tools of cultural anthropological approaches are ethnography—a study of a specific culture—and ethnology—the comparative study of cultures around the world.
Linguistic anthropology approaches focus on language use, meaning, patterns, structure, and evolution and how it shapes and is shaped by the human experience. archaeological anthropology the study of the patterns of behavior and the material record of humans who lived in the past biological anthropology the study of the biological and biocultural facets of humans and their relatives cultural anthropology the study of human culture in all of its complexity culture patterns of behavior human societies exhibit in their families, relationships, religions, laws, moral codes, songs, art, business, and everyday interactions ethnography the focused study of a culture or aspects of a culture ethnology the comparative study of many cultures linguistic anthropology the study of language use, meaning, patterns, structure, and evolution and how it shapes and is shaped by the human experience
17 Although we often describe anthropological investigations in terms of the specific area of focus, they are not actually separate lines of
inquiry; in fact, they are all intertwined. Anthropologists take an integrative approach in their study of humans, considering evidence from the wide range of approaches in our toolkits (Figure 1.2). It is only by investigating all these aspects that anthropologists have any hope of unraveling the complex, marvelous, and ongoing story of humankind. integrative approach the practice of drawing on all subdisciplines of anthropology, as well as other disciplines, to attempt to answer questions about humans ■ FIGURE 1.2 The four main areas of anthropology. They combine to form the integrative approach. Anthropologists also take a comparative approach in their work. They rely on specific studies to generate a large amount of information on one subject, and then they compare data and results across many studies, cultures, or populations. In this way they hope to understand, for example, the amazing array of similarities and differences we see in the human species and to determine if there are characteristics universal to
the human species and others that are found only in particular groups or societies. Anthropologists work collaboratively with other anthropologists and a wide range of other researchers and try to tackle questions at both the local and the global levels. comparative approach the practice of comparing features across entities/cultures/organisms to elucidate similarities and differences Anthropologists also take a historical approach, keeping in mind the contributions and insights of previous scholars in their fields and applying them to their own work. And they are well aware that all people, themselves included, see the world through the lens of their own culture. They strive, if not for objectivity—an impossible goal—at least for vigilance against cultural and personal bias as they observe and study human beings, either in their own culture or in other times and places. In this book we focus on biological anthropology, but you will see the other components of anthropology in evidence throughout the
discussions and examples. Biological anthropology itself can be divided into a number of subcategories. Probably the best known is paleoanthropology, the study of the fossils (the material evidence for past life) and fossil environments of past humans and nonhuman primates. Other biological anthropologists focus on the interconnections between human biological variation (such as differences in height, weight, and genetic patterns across different populations) and physiology, anatomy, disease, and demography. Still others look at the biological basis of behavior and how aspects of culture interface with biology and ecology (the interrelationships between living organisms and their environments). Finally, there are those who focus their studies on nonhuman primate species; they use the comparative approach to understand what is common to all primates, what is common to some primates, and what may be distinctive to humans. paleoanthropology the study of fossil humans and human relatives fossil
material evidence of past life on this planet
ecology interrelationships between living organisms and their environments Anthropology is a scientific discipline As a scientific discipline, anthropology shares certain characteristics with the other sciences. First, it requires that practitioners, students and professionals alike, use critical thinking, a certain way of approaching and thinking about information. Second, it can deploy the scientific method, a particular way of making observations, gathering data, and testing hypotheses. And finally, it operates through collaboration, a way of working together and building on work done by others. As you will see, critical thinking, the scientific method, and collaboration are recurring themes in anthropology, and they are three key themes in this book. We consider each of them in more detail in the next sections. Critical Thinking Is the Systematic Assessment of Information People today are bombarded with information via the media, the Internet, and even college classes; in
fact, we may be said to suffer from information overload. As educated people living in a contemporary society, we need to think about what we read and hear rather than accept everything at face value. In other words, we need to think critically. Critical thinking means active participation in the learning process. It means taking control of the information presented to you and examining it. It means asking, Where did this information come from? What part of this information consists of facts, or verifiable, observable truths? 18 What ideas and conclusions are being derived from those facts? What reasoning processes and assumptions were used to reach these conclusions; are they logical, or do they involve inconsistencies and false assumptions? In what form are the ideas and conclusions presented: Are they dogmatic assertions, or are they clear statements backed with logical arguments? Are nonfactual elements presented as facts? Does the person presenting the information have something to gain (or lose)
by convincing you to accept a certain viewpoint? What are the implications of the conclusions for different groups of people or for society in general? critical thinking taking control of information presented to you and examining it fact a verifiable, observable truth Let’s take a current example of this critical thinking questioning process. Some researchers today believe that there are inherent (or biologically based) differences in intelligence between the groups we (in the United States) refer to as “Asian,” “Black,” and “White.” What facts are provided to support this statement? Some standardized tests (such as the SAT) and some IQ tests show different average scores for these three groups. From these facts, these researchers conclude that there are inherent differences in intelligence among the three groups. What reasoning processes and assumptions lie behind these conclusions? The researchers make at least two assumptions: that the three groups are biologically distinct and that the tests actually measure innate cognitive
abilities (intelligence). They then argue that the differences among the groups can best be explained as biologically based. Is this reasoning process logical, or are there inconsistencies and false assumptions? CONNECTIONS See chapter 10, pages 317–325, for further detail on “race” and racism. The conclusions are based on false assumptions. For one thing, as we will see in chapter 10, the human species cannot currently be divided into large, biologically defined subunits (races or subspecies) labeled “Asian,” “Black,” and “White.” For another, exactly what aspects of biology are measured by standardized tests is not clear (although something, but not necessarily something biological, is definitely being measured, because people vary individually in their scores). Do the researchers’ conclusions have any implications for the groups in question or for society in general? Yes: If differences in test scores are primarily biological in origin, then social, educational, or economically based programs will have minimal impact on improving
the lower-end test scores. However, if these differences are not primarily biological, such programs may be effective. These two possibilities have significant economic, social, and political implications, and thus individuals making claims about this issue may have social, economic, and political motives. To evaluate complex arguments and issues like this one, you need to use your critical thinking skills. You also need relevant information. In chapter 10 we deal in much more depth with issues related to race, behavior, and human biological variation. Throughout the book we provide a substantial amount of information that you can use to critically examine a number of “hotspot” issues related to human variation. Beyond what you read here, you have access to nearly limitless information at the library, in classes, and on the Internet. If a particular topic intrigues you, by all means search beyond the introductory information given here and pursue it through the suggested readings and websites,
recommendations from your instructor, and even field trips to natural history museums or archaeological sites. Part of the goal of this book is to help you hone your critical thinking skills and build up your knowledge base so you can more easily distinguish opinion from fact, wishful thinking from valid argument, and belief from scientific practice.
Link of the original textbook (pdf):