…is all it takes to get some of the most recognizable of racial differences between human populations.

via steve sailer, from nicholas wade in the nyt:

East Asian Physical Traits Linked to 35,000-Year-Old Mutation

“Gaining a deep insight into human evolution, researchers have identified a mutation in a critical human gene as the source of several distinctive traits that make East Asians different from other races.

The traits — thicker hair shafts, more sweat glands, characteristically identified teeth and smaller breasts — are the result of a gene mutation that occurred about 35,000 years ago, the researchers have concluded….

“The first of those sites to be studied contains the gene known as EDAR. Africans and Europeans carry the standard version of the gene, but in most East Asians, one of the DNA units has mutated.

“Seeking to understand if the gene was the cause of thicker hair in East Asians with the variant gene, a team of researchers led by Yana G. Kamberov and Pardis C. Sabeti at the Broad Institute in Cambridge, Mass., decided to test the gene in mice, where its effects could be more easily explored….

“The Broad team engineered a strain of mice whose EDAR gene had the same DNA change as the East Asian version of EDAR.

When the mice grew up, the researchers found they did indeed have thicker hair shafts, confirming that the changed gene was the cause of East Asians’ thicker hair. But the gene had several other effects, they report in Thursday’s issue of the journal Cell.

One was that the mice, to the researchers’ surprise, had extra sweat glands. A Chinese member of the team, Sijia Wang, then tested people in China and discovered that they, too, had more numerous sweat glands, evidently another effect of the gene.

Another surprise was that the engineered mice had less breast tissue, meaning that EDAR could be the reason that East Asian women have generally smaller breasts.

“East Asians have distinctively shaped teeth for which their version of EDAR is probably responsible. But the mice were less helpful on this point; their teeth are so different from humans’ that the researchers could not see any specific change….

“A team led by Dr. Sabeti and Sharon R. Grossman of the Broad Institute has now refined the usual scanning methods and identified 412 sites on the genome that have been under selection. Each site is small enough that it contains at most a single gene.

Each race has a different set of selected regions, reflecting the fact that the human population had dispersed from its African homeland and faced different challenges that led to genetic adaptation on each continent. About 140 of the sites affected by natural selection are in Europeans, 140 in East Asians and 132 in Africans, the authors report in another article published Thursday in Cell….

so cool!

(note: comments do not require an email. east asians.)

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