On Valentine’s Day, the New York Times ran an article in its science section linking physical traits common in East Asians—thick hair, distinctively-shaped teeth, small breasts, and extra sweat glands—to a 35,000-year-old mutation in a gene called EDAR. Researchers reproduced the mutation, which is carried by East Asians but not Africans or Europeans, in mice. The animals had more lustrous fur, more sweat glands, and smaller chests.
The article, by Nicholas Wade, starts off with plausible explanations for why natural selection might have favored the deviation in EDAR when it emerged thousands of years ago in central China. One or two of the traits influenced by the gene may have been advantageous for survival; as those features persisted in the population, the other attributes came along for the ride. And he tracks down a reasonable hypothesis about which characteristic made EDAR so valuable: the sweat glands. For people hunting and gathering in China’s formerly warm and soupy climate, staying cool was crucial.
Fine. But then Wade derails the whole thing with a perfectly silly evolutionary biology just-so story. He quotes Joshua Akey, a geneticist at the University of Washington in Seattle, as saying it all comes down to pretty ladyparts.
According to Akey, “thick hair and small breasts are visible sexual signals which, if preferred by men, could quickly become more common as the carriers had more children.” In fact, he claims, “the sexually visible effects of EDAR are likely to have been stronger drivers of natural selection than sweat glands.”
Basically, the genetic mutation flourished because men wanted to do the no-no-cha-cha with women who carried it. Oops, I’d forgotten that science, the world, etc., revolves around what males find attractive. Never mind that this assumes an alarming passivity on the part of the females. Did they have no say in their mating partner? (That’s a rhetorical question: Studies throughout the animal kingdom show that it’s usually the females who decide who gets action and who doesn’t.) And even supposing that the women had no agency, were prehistoric East Asian men really so very picky? Did they typically refuse intercourse with large-breasted or fine-haired women? I am trying to imagine a caveman turning down a willing sexual partner on account of a triviality like insufficiently luxuriant tresses, and not just one caveman but the entire sperm-producing Pleistocene population.
To be fair, the paper itself, written by a team led by Yana G. Kamberov and Pardis C. Sabeti at the Broad Institute in Cambridge, Mass., largely avoids speculating about how the EDAR mutation perpetuated. “The problem with all selection, but especially sexual selection, is that it’s impossible to test on humans,” co-author Daniel Lieberman told me. “We were careful not to make assumptions about the selective benefits of the gene.” When I asked him whether he found Akey’s hypothesis plausible, he replied, “Frankly, no.”