tweaking just ONE gene…

…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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19 Comments

  1. Pleiotropy — a singlie variation in one geen can effect a plethora of physical and spychological traits, many of them seemingly unrelated. Ponder that. Quite a diffeent picture that if one gene controlled one trait, even though that trait might in turn effecct the expression of many other genes.

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  2. This is indeed cool. It gives hope that the genes for intelligence are small in number, and can be uncovered sooner rather than later.

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  3. “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.”

    Some of the commentators at Sailer’s blog pointed out that the reporter probably meant to write FEWER sweat glands, as East Asians tend to be less smelly than other peoples.

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  4. East Asians have fewer _apocrine_ sweat glands, but a higher density of eccrine sweat glands.

    As usual, the commenters on Sailer’s blog have no idea what they are talking about.

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  5. Roughly 50% of Koreans have no apocrine glands, whatsoever. That doesn’t stop them from smelling like garlic, though. -_- Kimchi packs a powerful punch.

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  6. I wonder if this mutation is neutral or if it gives some increased survival. Perhaps thicker hair and smaller breasts is an adaption to a cold climate. If they were in Central Asia at the time that is.

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  7. “It gives hope that the genes for intelligence are small in number, and can be uncovered sooner rather than later”

    My guess is it will turn out to be a few genes of big positive effect and *lots* with small negative effects.

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  8. East Asians have fewer _apocrine_ sweat glands, but a higher density of eccrine sweat glands.

    As usual, the commenters on Sailer’s blog have no idea what they are talking about.

    The interesting thing here to me is that EDAR370A basically seems to act more or less globally on many all glands, by increasing signalling as outlined on Chang et al (http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007591#pone.0007591-Zouboulis1) – Enhanced Edar Signalling Has Pleiotropic Effects on Craniofacial and Cutaneous Glands and in light of EDAR370A reducing the symptoms of Ectodermal Dysplasia – http://www.ncbi.nlm.nih.gov/pubmed/21916884.

    These glands may include apocrine glands.- no one seems to have bothered to check out what the effects of enhanced edar signalling are on apocrine glands alone (unless this is in Sabeti’s paper).

    In this light its interesting that the distribution of the East Asian ABCC11 “dry earwax” variant – which knocks out or reduces much apocrine function specifically – seems to basically match up in frequency with EDAR370A (although with the difference that ABCC11 seems to have a higher frequency, relative to EDAR370A in Europe and a lower frequency relative to EDAR370A in the Americas, or just South America).

    It seems like it might be plausible – although still needs testing – that EDAR370A increases some glandular function that East Asian ancestors “needed” (e.g. eccrine sweat) but with the disadvantage of increasing some apocrines function at the same time (including but not limited to increased stinkiness). And that ABCC11 “solved” this “kludge”.

    Anecdotally, I’ve read from some Caucasian people in Japan that Japanese (a population where EDAR370A and ABCC11 are both at slightly less than fixture, contrasted vis-a-vis Europeans who just don’t have EDAR370A at all and the dry earwax ABC11 at around 0.2 and Koreans where these are both at 1.0) generally don’t have any problems with BO, but there are some who REALLY have bad body odor.

    It’s interesting to consider that this might be do to an unusual combination of EDAR370A and the ancestral wet earwax form of ACC11 –

    e.g. “Straight Asian hair? Wet earwax? You’re gonna stink!”.

    Also, hbdchick, note that EDAR370A is also implicated in tooth shoveling! Talk about bang for buck (in terms of Asianness).

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  9. 7% of Han Chinese are homozygous for the African/European variant of EDAR, 370V. Then by Hardy-Weinberg, 39% are 370V/370A heterozygotes, and 54% are 340A/340A.

    Yet AFAIK, there’s no obvious phenotypic traits distinguishing these three genotypes — gather 100 Han, and you can’t pick out the 54 who appear really Asian and the 39 who look kinda Asian from the 7 who look like straight out-of-Africa.

    So if EDAR is super-important in establishing Asian-ness: why not?

    I think the answer is that EDAR 370A is one of many alleles at many loci that affect the traits in question. Perhaps EDAR 370A in a European background would have a noticeable effect on hair thickness, breast size, and sweat gland number. But in a typical Chinese background, its influence may be much more modest.

    Comments?

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  10. Yet AFAIK, there’s no obvious phenotypic traits distinguishing these three genotypes — gather 100 Han, and you can’t pick out the 54 who appear really Asian and the 39 who look kinda Asian from the 7 who look like straight out-of-Africa.

    Well, assuming the maximal interpretation of EDAR, 370V, the 7 would look really Asian as well (and yeah, I get straight out-of-Africa is hyperbole) – they’d have Asian pigment, stature, limb proportions, facial shape/flatness, body hair pattern. They just wouldn’t have the coarser hair, breasts would be larger and less firm all things being equal, not have shovelled teeth and have less agenesis of certain teeth (and that’s not that evident unless you look in the mouth), less sebum and less eccrine “watery” sweat.

    That said, at least one other allele difference is involved in Asian hair morphology, an allele of FGFR2.

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  11. Matt wrote, “Well, assuming the maximal interpretation of EDAR, 370V, the 7 would look really Asian as well.”

    Can you explain this a different way? I don’t understand the phrase “maximal interpretation.”

    I could imagine that Han Chinese 370V/370V homozygotes could tend towards thinner hair, bigger breasts, and more European-seeming teeth.

    It would be an interesting study, and given the simplicity of the initial genetics of the question — a single common SNP! — it seems like the sort of thing that 23andMe could tackle. And this SNP is sure to be included in Thousand Genome Project data, talk about hunting gnats with shotguns…

    Anyway, my point, such as it was, was augmented by the second paragraph of your 11:20am. EDAR 370A isn’t any sort of potent Asian-ness gene, given that Han Chinese without this allele still have a phenotype that’s very Han-Chinese-like.

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  12. Sorry, by “assuming maximal interpretation” I mean “even assuming EDAR370V explains all the phenotypic difference between the Asian and non-Asian average phenotype on the characters of hair morphology, shoveling morphology and breast morphology”.

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  13. @amac78 – “…gather 100 Han, and you can’t pick out the 54 who appear really Asian and the 39 who look kinda Asian from the 7 who look like straight out-of-Africa.”

    well, yeah — they’re not going to look like they’re straight out-of-africa — are they? — since the other variant is the african/european variant.

    actually, i’m often struck by how some east asians look less east asian to me than what seems like the average to me — i mean a lot less (although, truth to be told, i think i notice this more with japanese individuals than chinese) — so there is, i think, quite some variation in appearance. don’t know if i’m picking up on any differences due to this particular genetic variation, though. maybe it’s something else entirely.

    @amac78 – “I think the answer is that EDAR 370A is one of many alleles at many loci that affect the traits in question.”

    yes, i’m sure there are a bunch of genes related to “the east asian phenotype” (like the one that matt mentioned) — i just thought it was neat that here is one allele related to a bunch of them. cool stuff!

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  14. @staffan – “Perhaps thicker hair and smaller breasts is an adaption to a cold climate.”

    smaller breasts could be a sexual selection thing. i know that seems upside-down to all you guys who prefer big bOObs (~_^), but smaller breasts might make you look younger … younger=more fertile, etc., etc.

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  15. Thanks for clarification, Matt, and further comments, ‘chick. Fun discussion, I learned something.

    Reply

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