ch 3: This chapter puts humans in our evolutionary context, answering such “who questions” as we need to answer before investigating “how questions.” First, it explains where we fit in terms of broader patterns of primate evolution. Next, it shows how human behavior differs from that of other animals. Finally, it considers how we humans differ from one another. The most important differences among humans are cultural differences. Culture has several distinct properties for which we should expect to find evidence in the prehistoric record. Failing to find such evidence can suggest problems in our methods for investigating human evolution and prehistory.

Our young and originally tropical species Homo sapiens has spread, in an amazingly short period of time, to occupy more areas of our planet than any other animal species has ever contrived to do. Human beings reside on all five continents, and in virtually every environment that those continents have to offer.

Like every one of the many millions of other organisms with which we share our planet, the species Homo sapiens is the product of a long evolutionary history. The first very simple cellular organisms spontaneously arose on Earth close to four billion years ago, and their descendants have since diversified to give us forms as different as streptococci, roses, sponges, anteaters, and ourselves.

A description of some of the methods used in racial genetics and genomics is essential if we are to understand why claims have been made that modern genomics establishes the existence of race.

As scientific knowledge increased, the outward physical variation of humans on this planet posed a mystery to natural historians, and begged explanation. Why were there so many different “kinds” of people on the planet? If scientists could understand how this variation worked in nature, then perhaps, the reasoning went, we could understand why people appear different.

Why do some researchers care so much about race in their experimental designs? It is easy to understand why a racist forced by inherent bias would take this approach. But why would a nonracist biologist insist on doing racial science? As far as we can tell, there are two major reasons for this: medical expediency and the discovery of the genetic basis of complex traits. We would suggest that the first of these is a red herring, and the second a brick wall.

Research prior to human genomics opened several doors to race-focused research, but the availability of genomes was a game-changer. As we pointed out in Chapter 4, there is nothing inherently wrong in using racial or ethnic boundaries as research tools for trying to discover biological patterns within the human species – if they are justified.

A big part of the story of our species, and of how variation is apportioned within it, involves how our ancestors spread over the globe. After all, if we had simply stayed in our place of origin in Africa and not ventured out, there would be no question that we are a single entity. That is because if our species had been restricted to a single location (as many others are), two things would have ensured that differentiation into separate entities would not have occurred.

Humans have been roaming around the planet since the very beginning, encountering other humans in the process and doubtless forming opinions about them. And since human beings seem to have an innate urge to classify everything – doing which, after all, lies at the core of our way of mentally organizing and understanding the world around us – there is little doubt that, from the earliest days, our symbolic forebears categorized each other in some way.

As the nineteenth century dawned, the idea that species might not forever remain as the Creator had made them was no longer unthinkable. At one end of the range of possibilities was Buffon’s limited notion of within-species change; at the other was Lamarck’s vision of lineages transforming themselves through inner impulse.