Anthropology For Dummies. Cameron M. Smith

Anthropology For Dummies

subfields — but remember, discoveries in these individual fields have effects on the others.

Illustration courtesy of Cameron M. Smith, PhD

FIGURE 3-1: Anthropology as a four-field discipline.

Physical Anthropology and the Evolutionary Basis of Biology

One of Charles Darwin’s great contributions to civilization was to demonstrate that humanity was part of the world of living things, not separate from it. For thousands of years, Western civilization, backed up by the biblical story of creation, held humanity as a special creation fundamentally different from all other living things. By Darwin’s time, many were beginning to question this assessment, but the cultural pressure to conform to the dominant religion prevented most from saying so out loud. But Darwin’s ideas and the many it fertilized set the foundation for a new study: the study of humans as living, evolving creatures in many ways no different from the rest of animal life. Today, anthropologists have countless reams of data, much of it based on studies of DNA — the molecule that shapes all Earth life — that confirm the essence of Darwin’s claims, made back in 1859.

That evolutionary perspective allows the discipline of physical anthropology, the study of humanity as a biological phenomenon. What species are we most and least like? Where and when did we fist appear? What were our ancestors like? Can we learn about human behavior from the behavior of our nearest relatives, the chimpanzees and gorillas? Is our species still evolving? How do modern human genetics, population growth, and other current issues play out from a biological perspective? These are all issues that physical anthropologists investigate.

You say you want an evolution

The study of evolution is the study of the change through time of the properties of a living species. That’s because evolution is the foundation of the life sciences. Many kinds of life forms have become extinct (like the dinosaurs), but each of today’s living species (including humanity) has an evolutionary ancestry that reaches far back in time. Today, physical anthropologists can investigate our ancestors to tell us a lot about our evolutionary past.

Evolution is often called a theory by people outside the scientific community, but in 2008 the scientific community at large advanced evolution to a fact status. Evolution is well demonstrated and supported by a wide variety of evidence gathered by scientists from around the world over the last 150 years. Evolution does happen.

Evolution, like anthropology, is studied by scientists. The scientific method both subjects share is a relatively simple process of generating knowledge based on three main stages of investigation. First, the scientist makes observations about the relationships among variables (such as air temperature and its effect on water). She then forms a hypothesis, or a statement about what effects she believes those variables will have on one another. (For example, she may hypothesize that exposure to cold air will cause water to freeze.) To test her hypothesis, she performs experiments to see whether her predictions are correct. If her hypothesis holds up under this extensive testing, she accepts the hypothesis as fact; if the experiments fail to produce the predicted results, she rejects the hypothesis. The key here is experimentation. What matters isn’t whether the scientist is a professor or an undergraduate but whether the data support the hypothesis. Every scientific claim is entirely open to questioning and scrutiny. Science recognizes no authorities; every statement is open to further investigation. In this way, science is the most democratic way of generating knowledge.

Replication, variation, and selection

Until the mid-1800s, many questions about the human species, the age of the Earth, and other basic inquiries were answered by looking to one document: the Christian Bible. People argued that it contained all the answers humans would ever need, so no further investigation was necessary. The age of the Earth? An Irish archbishop calculated it as about 6,000 years, based on biblical chronologies. The origins of humanity? Clearly laid out in the first pages of Genesis: God created humanity in a moment of divine inspiration. Whatever one thinks of the morality prescribed by the Bible (and plenty of scientists use its messages as guides to their moral life), it’s clear today that these so-called facts are simply incorrect, dating from an age in which little was empirically known about the age of the Earth, the origins of humanity, or even that our own planet wasn’t at the center of the universe, but only one of many. For science, the interpretation of the universe could not proceed just as interpretations of biblical passages. New ways to investigate the world had to be invented. And one of the things they discovered was the evolutionary process.

Yes, the evolutionary process. Evolution is process, not a thing. In fact, it’s a single word used to describe the cumulative effects of three independent facts. Importantly, these attributes of evolution can be (and are) observed in nature, and the laboratory, every day. They are

Replication: The fact that life forms have offspring

Variation: The fact that each offspring is slightly different from its parents and siblings

Selection: The fact that not all offspring survive, and those that do tend to be the ones best suited to their environment

Figure 3-2 shows these characteristics in more detail.

Illustration courtesy of Cameron M. Smith, PhD

FIGURE 3-2: Evolution as the result of replication, variation, and selection.

Regardless of your personal views on the topic of evolution, the three processes of evolution aren’t arguable. Whether it’s in the form of zebra calves, salmon fry, or human infants, life forms replicate. Also, all offspring aren’t clones; variation occurs in small ways and significant ways, but it occurs. And if it weren’t for selection, the world would be swarming with every mosquito, beetle, and tadpole ever born; the fact that it isn’t verifies that not all of these creatures born survive into adulthood. Finally, it’s not arguable that the offspring best suited to their environment tend to pass their genes on to the next generation. And it is simply the cumulative effect of these processes that we call evolution.

When replication happens, the variable offspring are born into an environment that basically either selects for or against them; if two dragonflies are pursued by predators (like birds), the one with a better build for its environment is most likely to survive. It’s been selected for rather than against, and it’s therefore more likely than its less-fit sibling to pass on the genes that made it. Now the genes that made a fit dragonfly go on to make the next generation of dragonflies, which are slightly fitter than the parent generation. Essentially, that’s evolution: selection acting on the variable offspring, leading to the change through time of the characteristics of the organism.

It is the genes that direct the building of the life form that are passed on in the genetic code of sperm and egg cells. The whole body, of course, is not transmitted, but the instructions for building it are (in the incredible DNA

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