EDAR

There was a recent journal article about the East Asian variant of EDAR, v370 A. This variant influences the development of the ectoderm in many ways, and is responsible for many of the phenotypes characteristic of East Asia. In the study, they inserted this variant into mice in order to better understand its effects.

It causes increased scalp hair thickness, shovel-shaped incisors, an increase in the number of eccrine sweat glands, and smaller breasts.

For example:

images

Katy Perry does not have this EDAR variant, but Li Bingbing almost certainly does.

The authors modeled the spread of this allele, concluding that it conferred an advantage of about 7%, is about 30,00o year old, and originated in central China.  In my opinion, that estimate of the geographical origin is worthless, because moderate geographical differences in the strength of selection would completely bollix that calculation. Such differences often exist, especially for alleles that protect against infectious disease.  The date is reasonable, not least because the same variant is common in Amerindians.

Because the selected variant has so many different effects, it is hard to know which one conferred a selective advantage.  We probably don’t know all the effects yet: they found one new one, more eccrine sweat glands, in this study.

The authors certainly had trouble explaining the advantage.  They had several suggestions,  all silly. They suggested that more sweat glands might been useful in dissipating heat back in the Ice Age. One idea was that different effects had advantages at different times, but that’s wrong thinking.  The chance that any particular phenotypic  change confers a strong fitness advantage is very low:  by far the most likely case here is that one effect gives the advantage while others are close to neutral.

They suggested sexual selection: maybe East Asian men just like smaller breasts.  Of course any such fashion would have to have endured a very, very, very long time, about five times the length of recorded history. I’m not really sure that any such preference exists today.  I remember reading about the day that China relaxed the ban on foreign movies, back in 1979.  When they showed that first movie, virtually all activity in the Nationalities Hotel came to a halt. Waitresses, elevator operators, room boys, and interpreters all sat watching The Hunchback of of Notre Dame, starring Anthony Quinn and Gina Lollobrigida.

I would guess that the real advantage comes from an as-yet undiscovered effect of this highly pleiotropic variant. It has to be something that worked in a number of places, including the Americas, and over a long time period.

Advertisements
This entry was posted in Uncategorized. Bookmark the permalink.

48 Responses to EDAR

  1. Weston Beston says:

    Might it be Denisovan?

  2. Since the gene is expressed and produces quantifiable changes in a reproductive organ (the mammary gland), the knee-jerk guess would be that the survival advantage is linked to the role of that organ, namely, nursing/lactation. With changes of that magnitude, there’s a good chance that there are comparable changes in average breast milk production or composition.
    I can’t find any online data about overall production, but there’s one 1997 study that looked at its chemical composition. In that study, breast milk of Hong Kong Chinese women and women from a province in central China was compared against Western countries. Women from HK and women from central China had substantially different diets and different caloric intakes, but both groups had higher concentrations of long-chain polyunsaturated lipids DHA and AA than typical for Westerners.
    DHA in particular has a number of effects on brain development, it’s relatively hard to come by in the environment (its primary source is fish), and the efficiency of conversion of other polyunsaturated fats into DHA is low (except possibly in breastfeeding mothers.) If you have a gene that results in its greater concentration in breast milk, that will have a clear survival advantage in a society that subsists on a DHA-deficient diet.

  3. JayMan says:

    I’ve heard it said that East Asian men aren’t very interested in large breasts, and I thought that was silly (at least mostly silly). Anecdotally I’ve read that there is an emerging “big bust” genre in Japanese pornography.

    • Anonymous says:

      they are, as much as their western counterparts… but make no mistake, even with smaller breasts, Asian woman are perfectly able to compete with western women on the sexual selection battlefield. just look at what happen everytime west meet east: it it’s the western women that have trouble keeping their men interested, bigger breasts or not… yellow fever is not only the name of a tropical disease 😉

      • Sandgroper says:

        Sexual selection is rarely operating because, despite both men and women having their stated preferences, which are invariably purely visual, ultimately most men and most women find a mate and reproduce, albeit with someone who might not fit their stated ideal. So sexual selection just never comes into it, aside from assortative mating, which is more likely to be class-based or race-based.

        When I was young and single, my ideal girl was a blue eyed blonde with long legs. I had a whole string of blonde haired blue eyed long legged girlfriends. My pin-up girl was Goldie Hawn when she was in Laugh-In – a cute bubbly funny blue eyed blonde, but totally vacuous.

        I wound up marrying a Chinese girl who was notably not blue eyed or blonde haired, did not have particularly long legs, and was notably unbubbly – in fact she was depressingly serious, thoughtful and responsible. And as flat as a board. When she was dressing for our wedding, my mother said “You should really wear a padded bra with that dress, dear” and my wife responded “I’m wearing one.”

        Not because I had to, but because when it came down to it, on the level of sexual attraction, things are happening that we may not be aware of – it’s not just a straight out visual thing. Chemistry is a biggie. Subtle scent cues, stuff like that. Personality, character, intelligence. And when it comes to something as serious as marriage, non-sexual factors come into it big time – like seeing eye to eye on the really big issues in life that matter and are likely to determine whether you stay married or not.

        I agonised for years over whether I should marry this blonde or that blonde…within 3 days of meeting my Chinese wife-to-be, I knew she was The One. And I was as shocked as anyone, because I had simply never contemplated marrying someone of another race before. She took somewhat longer to convince, I might say – years, rather than days. But the thought of marrying a ‘foreigner’ came as a total shock to her too.

  4. Tom says:

    There was an article recently saying that large breasts aren’t popular in North Korea, and that similar views used to exist in Japan and China:

    http://www.examiner.com/article/north-korean-women-forced-to-hide-their-large-breasts

    • Greying Wanderer says:

      If true that might fit with the breast-feeding angle i.e. 100 men and women on an island and 50 of the men like small breasts and 50 like large breasts then if small breasts confer an advantage over time in one environment – because of the DHA thing – and if the preference for small or large breasts is inherited then the men who are attracted to smaller breasts will have more descendents and eventually you might get 90% liking small breasts and 10% large.

      • Digging in Google Scholar turns up a few articles from the 80’s positing that women accumulate fat in their breasts to send deceptive signals to males about their ability to produce milk.

        Articles mention that, as far as their authors are aware, having large breasts does not seem to translate into having more milk (in developed countries), but argue that what’s true for a well-nourished woman trying to breastfeed for 3-6 months in the U.S. may not necessarily be true for hunter-gatherers breastfeeding their young for 2-5 years after birth.

        One part of the issue here is that permanently large breasts themselves are a relatively novel feature. For example, female chimps have flat breasts unless they are pregnant or lactating. As to when and why humans evolved large breast fat deposits, scientists don’t seem to have an agreement yet.

        It could go both ways: large fat stores in breasts could be beneficial if the woman has an unstable food supply; smaller stores could be beneficial if the food source is stable but generally deficient in stuff like DHA (whose synthesis is upregulated elsewhere in the body during lactation.)

      • JayMan says:

        @Eugene:

        How large human breasts got started is one thing. But Satoshi Kanazawa examined how male sexual attraction to them evolved.

      • Ha. Marlowe. I was just looking at that exact article half an hour ago.
        I think there is a difference between what Marlowe really says and how Kanazawa represents his view. I actually find Marlowe’s argument unpersuasive. He says that large breasts give the woman a reproductive advantage by serving as a signal of large residual reproductive value. In his own words, “the hypothesis is contingent upon considerable female-female competition for mates.” It’s a pretty weak case, the existence of said competition or of the reproductive advantage from winning the competition seems questionable. And once the woman ages a bit, the same signal starts working against her by advertising that she’s older than competition. This would make it harder for older women to find mates if the original mate is somehow lost.
        On the other hand, Kanazawa makes a lot more sense. Women may have evolved large breasts for some purely practical reasons, but, once they did, it made sense for men to be more attracted to large, firm breasts, indicating youth (as opposed to large, sagging breasts, indicating old age, or small, inconspicuous breasts, providing no information on its owner’s age.)

    • JayMan says:

      You’d be surprised what men crave when they don’t know what’s out there…

  5. IC says:

    Taste for large breasts is learned one in East Asia. Personal anecdote.

  6. George says:

    There is definitely variation in preference for butt size. Black men have a preference for large butts that generally isn’t shared by white men.

    There has been recently a mainstreaming of the preference for large butt sizes due to the increase in black influence on mainstream and pop culture, and white male preference for larger butts may have increased, but the difference between white men and black men regarding butt size preference seems to persist.

    There could be variation in breast size preference among different groups as well.

    • JayMan says:

      As much as this is true (and as far as I know it hasn’t been concretely studied), I doubt White preference has changed much. I suspect that it’s just that the ones that appreciate ample female rear ends are more open about it.

      • George says:

        If there has been a change, I don’t see why it would be due to greater “openness” as opposed to any other of the myriad things that have correlated with the change. “Openness” seems to be a catch-all explanation for everything and anything. I don’t think “openness” has ever been teased apart from all the other correlations before being used to explain all sorts of things. You see “openness” frequently used to explain homosexuality for example.

      • JayMan says:

        George, I think the “openness” you’re talking about is something else. I almost said “vocal” instead of “open”.

        “Openness” is a major dimension of personality…

      • George says:

        Yes, I was thinking of the argument that greater social permissiveness allows latent preferences or orientations that always existed to be expressed. Isn’t that sort of what you’re saying? “Openness” as a dimension of personality is used to mean something like an inclination towards experiencing things one doesn’t necessarily prefer or favor.

      • JayMan says:

        @George:
        “Yes, I was thinking of the argument that greater social permissiveness allows latent preferences or orientations that always existed to be expressed. Isn’t that sort of what you’re saying?”

        Yes. And I believe that this is the case, with the caveat that certain sexual proclivities were probably rarer back in the day because the lack of mass media prevented the susceptible from discovering them.

      • George says:

        Right, this is the “openness” argument that’s used to explain everything from homosexuality to coprophilia. It’s even been used to explain prison rape: http://usatoday30.usatoday.com/news/nation/2006-01-17-prison-rape_x.htm

        Apparently it’s in the “open” environment of a locked-up prison cell that latent preferences for being raped that always existed are finally allowed to be “discovered” and expressed.

        Like I said, “openness” is a catch-all explanation for everything and anything. I don’t see why anything would be due to greater “openness” as opposed to any other of the myriad things that have correlated with a change. “Openness” has never been teased apart from all the other correlations before being used to explain all sorts of things.

    • Miley Cyrax says:

      It seems that all men prefer shapely asses with thin waists.

      But life is full of trade-offs.

      Bigger butts also mean thicker waists, ceteris paribus.

      Perhaps black men just have less of an aversion to female obesity, due to less discriminating tastes (higher sex drive and/or higher testosterone), fewer options (people tend to date with others of their own race, and the female obesity rate is highest among blacks), or having been surrounded with a greater degree of female obesity all their lives. Or some combination of all these factors.

      I suppose “I am less averse to thicker waists and I cannot lie, you other brothers can’t deny” has less of a ring to it.

      • Miley Cyrax says:

        It’s even lamp-shaded within that song: “when a girl walks in with an itty-bitty waist, and a round thing in your face…”

  7. George says:

    There was a recent study of white British men that indirectly tested breast size preference. Apparently the most preferred breast size was “medium”:

    http://www.theatlantic.com/health/archive/2013/03/men-who-idealize-large-breasts-are-more-likely-hostile-toward-women/273931/

  8. dave chamberlin says:

    It certainly appears we will develope a very extensive list of alleles that we know have conferred x amount of advantage but we won’t know why. Dr Frankenstien in Elbonia doesn’t have to why they caused an advantage he just wants to know what the effect is when they are all combined. Hopefuly the result is a whole lot more impressive than small tits, thick hair and extra swaet glands.

    • IC says:

      Larger breasts carry higher risk of breast cancer.

      • Matt says:

        Breast density, which is actually promoted by the Asian EDAR allele, is actually an increased risk factor for breast cancer.

        Having dense breasts — that is, relatively little fat in the breast and more glandular and connective tissue, as seen on a mammogram — is one of the strongest known risk factors for breast cancer.

        Women with dense breasts have been shown to have a four- to six-fold increased risk of developing breast cancer; only age and BRCA1 and BRCA2 mutations increase risk more.

        So promoting smaller breasts through a mechanism that increased density – that would achieve the opposite end to reducing breast cancer risk.

        Fortunately for East Asian women, ABCC11 has strong negative associations with breast cancer, which (possibly in concert with other variants) more than cancels out any potential increase in breast cancer risk.

      • Matt says:

        For: ABCC11 in my post read “the East Asian modal allele of ABCC11” (the dry earwax allele).

        Also, interestingly, the association of the East Asian modal allele of ABCC11 with reduced breast cancer risk seems to hold up much better in the East Asian population (basically in all the Japanese studies done), where the East Asian EDAR allele is present, with less impressive to no replication in Western populations (where ABCC11 is a minor allele, but still at far greater frequency than the East Asian EDAR allele).

        http://link.springer.com/article/10.1007%2Fs10549-010-1292-2 – “No evidence for an association between the earwax-associated polymorphism in ABCC11 and breast cancer risk in Caucasian women”

        http://link.springer.com/article/10.1007%2Fs10549-011-1613-0 – “The earwax-associated SNP c.538G>A (G180R) in ABCC11 is not associated with breast cancer risk in Europeans”

      • Susceptibility to breast cancer would be an extremely marginally selected trait anyway. In the modern world, lifetime incidence of breast cancer is somewhere on the order of 10%, and the fraction of all cases that occurs in premenopausal women is in single digit percentages. And even cases that do occur in premenopausal women, predominantly occur in the last 5 years before menopause. In the U.S., women are currently recommended to start regular mammograms at age 40 and there’s been some debate on the efficacy of that: it’s been claimed that 40 is too early and wasteful and we should change that to 50.
        Even, say, a 50% increase in overall rates would result in new cases in ~0.5% premenopausal women, which would mean a ~0.1% reduction in expected lifetime number of births for a woman carrying the gene, and some small hit (likely of comparable magnitude) to expected survival of her children.

  9. bruce says:

    Fat knockers get jiggy with lactose tolerance? But the yellow fever hypothesis seems more likely. Asian chicks are bred to be an asian hero’s wage: youthfully thick hair, juicy glands, strong teeth that yet aren’t creepily carnivorous.

  10. Perhaps permanently-swollen breasts were developed to camouflage fertility cycles, making it difficult for males to determine which females are in heat; keeping social status up for a longer portion of the pregnancy.

  11. Skittles the dancing wallaby says:

    Are you sure that there is no advantage to additional sweat glands?

    Supposedly East Asians have significantly more Neanderthal ancestry than Europeans, approximately 40% more.* But Neanderthals didn’t live in East Asia, as far as we know. (And East Asians aren’t any more Denisovan than Europeans.)

    Neanderthals evolved in a cold climate for hundreds of thousands of years, so they may not have been particularly good at sweating.

    According to the NYtimes article, the mutation supposedly arose 35,000 years ago in a hot and humid area in central China. (The full text journal article isn’t available.) 35,000 years ago is the twilight of the Neanderthals. Hybridization with Sapiens would either be ongoing or something that happened in the relatively recent past.

    So it makes sense doesn’t it?

    A population of Sapiens hybridizes with Neanderthals in a cold region and inherits some of the Neanderthal temperature regulation system which is efficient in cold climates, but inefficient in warm climates. That population later moves into warmer areas and fortuitously picks up the mutation we are discussing here, allowing them to regulate their temperature and survive better in this new warm area. This population eventually becomes isolated and makes it out to East Asia where they become… East Asians.

    *http://www.genetics.org/content/early/2013/02/04/genetics.112.148213.full.pdf+html

    • misdreavus says:

      I don’t buy it.

      It would be very strange indeed if that advantage persisted everywhere from the Arctic Circle to Tierra del Fuego.

    • Matt says:

      Neanderthals evolved in a cold climate for hundreds of thousands of years, so they may not have been particularly good at sweating.

      Perspiration is quite a bit less efficient in clothing than without. So you might want to uprate your sweating rate if you habitually have to exercise while wearing heavy gear. Although the Neanderthals probably wore skins, it may have been more clothes than were habitually worn (at least for warmth) than the contemporaneous African hominids (or maybe not – they might have been heavy panters, they theoretically have a breathing apparatus optimised for lots of breathing with little moisture loss).

    • anonymous says:

      The adaptive account Sabeti and co arrive at here is hugely dependent on the climatological and center-of-origin models checking out. I’m inclined to doubt that they’ve hit the nail on the head.

  12. Matt says:

    Point of interest, which I kind of noted at the time this paper went out, I think its interesting that the Asian derived EDAR allele seems to uprate pretty much all kinds of glandular development, while the Asian derived ABCC11 seems to knockout specific kinds of glandular function.

    It would be interesting to compare the timing of the selective sweeps, to see if one of the changes is follows the other (e.g. EDAR leads and ABCC11 follows) or whether they occur contemporaneously.

  13. bruce says:

    Shovel teeth and more sweat glands might both reflect a more vegetarian diet. Vegetarians fart more and stink less. Vietnamese used to say they could smell the — across a rice paddy (full of human (Vietnamese) fertilizer).

    • anonymous says:

      Come on, look at the distribution of incisor shoveling. More vegetarian like the Buryats and Evenks and Fuegians and Comanches? Read what C. Loring Brace has to say…

      • bruce says:

        Comanches were vegetarians (corn-growers, not hunters) before their brief horse/ slave empire, there were never all that many Fuegans; as for C Loring Brace and his chopsticks? Well, don’t you spend less time picking meat out of your teeth than chomping slowly over veg? And I stand by ‘vegetarians fart more and stink less’.

        Might have me on Buryats and Evenks. Maybe fish, not veg? Eat fish, sweat out fish oil?

  14. Tooth is Stranger than Friction says:

    I would guess that the real advantage comes from an as-yet undiscovered effect of this highly pleiotropic variant. It has to be something that worked in a number of places, including the Americas, and over a long time period.

    Something that works well everywhere and over a long time is intelligence. So if it confers a cognitive advantage, a) that explains it; b) that explains why the effect hasn’t been discovered. Researchers know that you can’t look for things that aren’t there. ‘Coz genes don’t code for intelligence in human beings and haven’t since approx. 06:17 GMT, November 23rd, 142,788 BC.

  15. Toad says:

    “they inserted this variant into mice in order to better understand its effects”

    Are you thinking what I’m thinking?

  16. Jim says:

    The Comanches began as a Shoshoni band which migrated into the West Texas Plains about 1700. After the Pueblo Revolt of 1680 temporarily drove the Spainish out of New Mexico the Pueblo Indians came into possession of a large number of horses. These horses were acquired by trade and/or theft by Southern Athabascans recently arrived in the Southern Plains from Canada. The Southern Athabaskans became the first “classic” horse-riding and buffalo hunting Plains Indians. They were joined by the Kiowa a tribe from the Taos Pueblos. A Shoshoni band who became the Comanches arrived about 1700 and succeeded into pushing the Southern Athabascans to the south and west.
    The original Comanches were presumably little different from the other Shoshoni and other Indians of the Great Basin. However over the next 150 years the Comanche raided extensively over Texas and well into Mexico. They took many captives in these raids and I have read that their genetics were quite significantly changed by the influx of captives. Their greatest leader Quanah Parker was the son of a white women captured as a child. So their present day genotypes could be quite a bit different from that of the original Shoshoni band entering the Southern Plains in 1700.
    It is true that after 1700 the Comanches almost certainly ate far more meat than their ancestors had done before that time. They hunted not only buffalo but also rustled large numbers of cattle from cattle ranches. They drove the cattle north to their home territory where in addition to eating the cows themselves they also traded large numbers of cattle to white traders who drove them east to supply the US beef market. I have read that in the early 19th century the Comanche were the principal suppliers of beef cattle to the US market.
    The Comanches took many captives in their raids. I have never read about them having “slaves”.
    They raided over a huge area but as they never attempted to rule over it I wouldn’t call it an “empire”.

    • bruce says:

      I guess you’d prefer ‘brief period when they took many captives and sold them for guns and metalwork over a huge raiding area they never attempted to rule over’ to ‘brief horse/slave empire’.
      The distinction encloses little difference. Horse empires like the Mongols or Comancheria weren’t like the Roman siege infantry empire.

  17. Pingback: Phenotypes vs genetic statistics | West Hunter

  18. dlr says:

    Wikipedia says that eccrine sweat glands release antimicrobial peptides (e.g. dermcidin).

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s