Sunday, September 26, 2004

Race discrimination

Via Gene Expression, Richard Dawkins on
Race and Creation
Our recent worldwide diaspora out of Africa has taken us to an extraordinarily wide variety of habitats, climates and ways of life. It is plausible that the different conditions have exerted strong selection pressures, particularly on externally visible parts, such as the skin, which bear the brunt of the sun and the cold. It is hard to think of any other species that thrives so well from the tropics to the Arctic, from sea level to the high Andes, from parched deserts to dripping jungles. Such different conditions would be bound to exert different natural selection pressures, and it would be surprising if local populations did not diverge as a result. Hunters in the deep forests of Africa, South America and southeast Asia have all become small, almost certainly because height is a handicap in dense vegetation. Peoples of high latitude, who, it has been surmised, need all the sun they can get to make vitamin D, tend to have lighter skins than those who face the opposite problem - the carcinogenic rays of the tropical sun. It is plausible that such regional selection would especially affect superficial characteristics like skin colour, while leaving most of the genome intact and uniform.

In theory, that could be the full explanation for our superficial and visible variety, covering deep similarity. But it doesn't seem enough to me. At the very least, I think it might be helped along by an additional suggestion, which I offer tentatively. We are indeed a very uniform species if you count the totality of genes, or if you take a truly random sample of genes, but perhaps there are special reasons for a disproportionate amount of variation in those very genes that make it easy for us to notice variation, and to distinguish our own kind from others. These would include the genes responsible for externally visible "labels" like skin colour. I want to suggest that this heightened discriminability has evolved by sexual selection, specifically in humans because we are such a culture-bound species. Because our mating decisions are so heavily influenced by cultural tradition, and because our cultures, and sometimes our religions, encourage us to discriminate against outsiders, especially in choosing mates, those superficial differences that helped our ancestors to prefer insiders over outsiders have been enhanced out of all proportion to the real genetic differences between us. No less a thinker than Jared Diamond has supported a similar idea in The Rise and Fall of the Third Chimpanzee. And Darwin himself more generally invoked sexual selection in explanation of racial differences.

2 Comments:

Blogger Greyshade said...

This is (I hope) pretty much received wisdom in modern humanevolutionary science. It's interesting to note that melanin depletion (lighter skin) does not appear to have evolved in any sub-Saharan African population despite the longer evolutionary history and greater genetic diversity of this continent so the vitamin D theory may correctly identify the "trigger" for this adaptation.
Of course there are many other morphological differences between African tribes - many of them, no doubt, at least as prominent as skin-colour to a non-eurocentic eye.

26 September 2004 at 2:49 PM  
Blogger Sock Thief said...

Do you mean the environmental adaptation theory is received wisdom or the sexual selection Drawkins talks about?

26 September 2004 at 5:17 PM  

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