Free Wired for Culture: Origins of the Human Social Mind by Mark Pagel Page A

vehicles, and it is important to see them as not different in principle from biological vehicles, it is just that the information on which they are based takes a different form: it resides in our minds rather than in our genes. Thus, when people walked into the Arctic and survived, it was because they had acquired the knowledge and technology to make clothes suitable to that harsh environment, to build shelters out of ice, and to fish in the cold Arctic waters. At a later time and different place, when Polynesian people invaded the Pacific, it was because they had acquired the technology to produce seagoing boats, and the knowledge of how to navigate by the stars.
    Indeed, we can think of our differing cultural survival vehicles as playing the same ecological role as different biological species. Just as a camel would make a poor musk ox, a Polynesian would not be well equipped to survive the Arctic. But of course our cultures can adapt on the fly and without having to wait for genetic changes to come along, and so the rapid spread of our various cultural species around the world after we left Africa is like a tape of biological evolution speeded up a millionfold or more. Almost everything around us today in our modern world can be attributed to social learning and the cumulative cultural adaptation it propels.
    This is not to say our genes played no role in our occupation of the world, just that it was our cultures that took us to its various environments to begin with. When people walked into the Arctic, they began to evolve genetically to have a stocky build that made them better at retaining heat, but it was their culture and not their genes that took them to the Arctic to begin with. Similarly, the Polynesians would also adapt genetically to their hot and sunny environment by becoming leaner and darker-skinned, but again it was their culture that got them there.
    Modern genomic studies of large numbers of people are discovering many small genetic differences among human groups that confer some sort of advantage in their environments. For example, in some European and African societies with a long history of dairying, adults have acquired the ability to digest milk. We have seen how some Tibetan people have acquired an extraordinary capacity to extract oxygen from the air at high altitudes, and how some Han Chinese have an unusual ability to metabolize alcohol. Hunter-gatherer groups exposed to more starch in their diets produce more salivary amylase—an enzyme that begins the process of digestion while food is still being chewed—than those whose diets contain less starch. Differences in facial appearance around the world might be related to arbitrary preferences in the choice of mates.
    These are just some of the many small genetic differences among human groups that have arisen as a result of being thrust into environments that our cultures opened up to us. And it is remarkable how quickly we have adapted. The 60,000 to 70,000 years since modern humans spread out of Africa is little more than the blink of an eye when stacked against the 6 to 7 million years that separate us from our Great Ape ancestors. The presence of these genetic differences, however small, tell us that we have had a habit of keeping to ourselves as we spread out around the world, because had we not, our genetic differences would have become blurred. This is not to deny that human groups have always traded with each other, intermarried, fought wars, and traipsed across each other’s territories. But it is only by having a tendency to maintain our identities in separate cultures or tribal groups that natural selection could have sculpted our many differences, and have done so in just the few tens of thousands of years since we walked out of Africa. Then again, we might have guessed this was the case: how else but through a tendency to keep to ourselves in our cultural survival vehicles can we explain a single species that speaks at least 7,000