Dr. Diamond again.
What a wonderful find (and this is a genuine, first-hand excavated link; I didn’t get it from Boing-Boing or nothin’). It’s a video lecture from Jared Diamond on the origins of human geographic variation (aka “race”).
His core argument is beautifully simple. Three selective forces shape species. The first, and most famous, is natural selection–the external forces that make for many ways of being dead and only a few ways of being alive. Then there’s sexual selection–the fact that offspring resemble their parents, and therefore successful mates will cause the general population to look more like them. And, last, there’s neutral selection–features that neither help nor hurt an organism, and therefore gradually grow more different, like fingerprints.
He says that 19th-century eugenics pegged geographic variation as a result of natural selection, claiming that people near the equator developed dark skin to protect against the sun, and people near the poles developed light skin to compensate for a deficiency in sunlight. (Right away, insidiously, this theory gives us an inexorable division in the human species.) Diamond throws this out on two counts–first of all, skin cancer and vitamin-D deficiencies tend to kill us long after we’ve reached reproductive age, if at all, so they’re very weak selection factors, especially when you consider the short life expectancies of early humans. And second, we don’t actually see a consistent distribution of the darkest-skinned people near the equator and the lightest-skinned at the poles–although the assumption has been repeated so often for the past few hundred years that most of us assume it’s true.
Instead, he argues that our variation comes from sexual selection–when people spread geographically, the small first wave of people that settled in each new territory (”The first people across the Bering Strait, the first people across the English Channel”) exercised an outsized influence over the superficial appearance of their descendants. Sexual selection is the opposite of natural selection; instead of producing functional differences that help us survive, it’s the preservation of arbitrary differences in successful survivors. (After all, says Diamond, “Nobody [in eugenics] can explain the survival value of red hair in Ireland, when Britain has pretty much the same climate”).
And there’s a fascinating discussion at the end in which he mentions that, thanks to advances in transportation over the past few thousand years, we’ve already been doing a lot more “intergeographical dating” than we realize. Large statistical studies of married couples around the world have revealed that, even when the pair appear to belong to different ethnic categories, they’ll commonly have matched features like proportional fingers, eyes, or earlobes, suggesting that their ancestors have already swapped some genes….