A more plausible conception of race, one that is consistent with how careful philosophers and geneticists use the term, recognises that: When humans began leaving Africa around 75,000 years ago, they dispersed across a much greater range of environments than they had previously inhabited. The humans that settled in different geographic regions subsequently came under different selection pressures (e.g. temperature, seasonality, altitude). Natural barriers such as oceans (e.g. the Atlantic), deserts (e.g. the Sahara) and mountain ranges (e.g. the Himalayas) impeded gene flow between different populations for substantial periods of time. When there is limited gene flow between populations that have come under different selection pressures, we would expect them to gradually diverge from one another over via the processes of genetic drift and natural selection.
Geography as Destiny
The idea that environmental and geographic circumstances, rather than inherent traits of peoples, determine the divergent fates and development of human societies.
The primary reason that natural philosophers began to classify humans into different races is that human populations look different from one another. Their skin colors, hair textures, facial structures, and stature all differ, often in predictable ways. Furthermore, these differences reflect their divergent geographical origins. In fact, researchers can classify human variation by continent quite accurately using only data from the human skull. (They are able to correctly classify human skulls into black and white Americans with about 80% accuracy, using only two variables.) Therefore, despite the common charge that racial classification is ipso facto racist, and that most Enlightenment typologies of human variety were motivated by prejudices and a desire to rationalize imperial domination, ordinary people and Enlightenment philosophers also took to classifying human differences for the mundane reason that such differences actually exist.
History followed different courses for different peoples because of differences among peoples’ environments, not because of biological differences among peoples themselves.
The social scientists’ official view of race is designed to support the political view that genetics cannot possibly be the reason why human societies differ—the answer must lie exclusively in differing human cultures and the environment that produced them. The social anthropologist Franz Boas established the doctrine that human behavior is shaped only by culture and that no culture is superior to any other. From this point of view it follows that all humans are essentially interchangeable apart from their cultures, and that more complex societies owe their greater strength or prosperity solely to fortunate accidents such as that of geography.