Where are the freaks?

Share on FacebookShare on Google+Email this to someoneTweet about this on Twitter

So I’ve been mulling over the recent publication in Annals of Human Genetics of a review of the recent skin color genomic work. The conclusion is pretty predictable given the recent findings:

a) Dark skin is the modern human ancestral trait
b) Light skin is derived
c) The derivations are independent

There is lots of stuff to comment on, but I’ll limit myself to a weird thought I’ve had for a while. The authors point out that East and West Eurasians (e.g., Western Europeans and Chinese) are light, in general, because of different mutations on different loci. In other words, the genetic architecture is pretty dissimilar. Even in the one case where the same locus (or genomic region) was subject to selection the haplotype differed. One would expect that there would be overlap in some of these genes being selected for since they are implicated in the same phenotype, though the allelic solution was distinct. Nevertheless, my interest is in the loci which do not overlap (most). Consider SLC24A5. It explains around 30% of the intergroup variance between Europeans and Africans, but none of the variance between East Asians and Africans, because East Asians and Africans share the ancestral allele. In contrast, MC1R is hyperpolymorphic in Europeans, constrained to the ancestral state in Africans, and being positively selected in East Asians toward fixation. And so on. Now…imagine, you have loci:

1, 2, 3, 4, 5, 6, 7, 8

…implicated in the loss of melanin production in human skin. Europeans are derived on:

1, 2, 3, 4, 5 (so ancestral on 6, 7, 8)

East Asians on

5, 6, 7, 8 (so ancestral on 1, 2, 3, 4)

Assuming that the loci are fixed, if you crossed a bunch of Asians with a bunch of Europeans (here’s looking at you Hawaii!), after a few generations you could have someone who is derived on:
1, 2, 3, 4, 5, 6, 7, 8 homozygously

Greg points out that these selected genes seem to be relatively recent (agricultural?), so their shallowness means they aren’t embedded in coadapted complexes which are likely to birth monsters. In fact, we know from pedigree studies that between Europeans and Africans skin color is inherited pretty much in an independent and additive fashion with 4-5 loci accounting for 90% of the between racial variance. So I am wondering if any intrepid readers want to engage in skin reflectance tests of variously racially mixed happas in Hawaii?

21 Comments

  1. There’s a decent amount of Polynesian DNA floating around in Hawaii, and they’re definitely darker than NE Asians and split off phylogenetically pretty early. You could always cast a wide net and toss out data whose neutral markers showed non-trivial Polynesian admixture — but if the loci you’re interested in are under selection, the person may have retained the Polynesian alleles there but lost the neutral Polynesian ones due to drift, which would make this project difficult. 
     
    You’d probably have better luck with NE Asian / Euro hybrids along the Pacific coast. The NE Asian immigrants there are very recent, and there are no other groups to muddle the picture… some chance of Af-Am descent among the Whites, I guess. If you were really anal, you could do this with almost zero trouble in Europe using Whites and recent NE Asian immigrants. 
     
    One thing I’ve noticed about the light skin of Eurasians is that, even when it’s light / pale, it has more of a sheen or glow (I don’t know how to properly describe it). It’s not like the pasty pallor of a pale Irish person. That could be due to the texture of the skin, though, not the color… lots of work to be done anyway!

  2. assman, there are like 10X more east asians in hawaii than native hawaiians. are you so east coast you don’t know that? :-) so that’s what i mean…

  3. 10X more east asians in hawaii than native hawaiians 
     
    According to US Census data at the Wikipedia entry for Hawaii, in 2005 Asians made up 57.53%, American Indians or Alaskan Natives made up 2.03%, and Native Hawaiians or Pacific Islanders made up 22.1%. So there are less than 2.5 times as many Asians as PIers and Amerindians. It says that ~20% of Hawaii is mixed, and you figure a fair amount of that includes the PI and Amerindian pops. Seems like a reasonable objection someone could raise during peer review or public discussion, so it might be worth it to look instead at the Eurasians along the Pacific Coast. 
     
    are you so east coast you don’t know that? :-)  
     
    At least we don’t talk like Valley girls!

  4. USA census site
     
    Asian persons, percent, 2005 41.5%  
    Native Hawaiian & Pacific Islander, percent, 2005 9.0% 
     
    the 9% includes a lot of mixed people, including a fair number of people who are more east asian than native hawaiian, but the economic benefits are pretty big if you are a “native.”

  5. the data above is for ‘one race’ according to the detailed page.

  6. Or perhaps most interestingly…. what if all the Euro-ancestral genes (6, 7, 8) are inherited from the primarily European parent and the Sino-ancestral genes (1, 2, 3, 4) from the primarily East Asian parent? And assume that a 5 has been aquired somewhere. 
     
    Two white parents, one black kid with partial epicanthic folds.

  7. You guys have obviously never painted a house. Colour (OK, color then) – shade – texture – why do you think Jablonski used light reflectance as a single measurable property? 
     
    And since when are Chinese ‘East Eurasians’, Razib? You’re trying to confuse me now, aren’t you? 
     
    If you want to strictly measure differences in skin reflectance between East Asians, West Eurasians and people of mixed descent from those two groups without risking confounding factors, you’d actually be better off going outside of the USA, although I realize that very concept is probably abhorrent.

  8. And since when are Chinese ‘East Eurasians’ 
     
    Since Leibniz. :)

  9. But Leibniz believed in intelligent design. Sort of. Well, I suppose Newton must have too. People did in the dark ages. 
     
    I still think Eurasian should be Indo-European. I know that’s a term reserved for languages and it is not a one to one correspondence, but it seems a lot more self-explanatory to me.

  10. The word is “hapa.” It’s the Hawaiian pronunciation of “half”. Based on happenings (hapa-nings?) at the Wikipedia article on “hapa”, there seem to be a number of Native Hawaiians who believe that you can be a hapa only if you’re part Hawaiian. But they would seem to have lost control of the word, which is increasingly used as a term for part-Asian on what we here in the islands call “the mainland.”

  11. Karen, yes, they’ve hijacked ‘hapas’ to mean Eurasian. Maybe that’s because they’ve pinched Eurasion to mean Indo-European. 
     
    Mainlanders.

  12. “One thing I’ve noticed about the light skin of Eurasians is that, even when it’s light / pale, it has more of a sheen or glow (I don’t know how to properly describe it). It’s not like the pasty pallor of a pale Irish person. That could be due to the texture of the skin, though, not the color… lots of work to be done anyway!” 
     
    This is likely not due to pigmentation but to the fact East Asians have more fat under their skin than whites…which also gives that “younger” look, as well as the predominant “yellowish” color, although some East Asians are naturally ghostly white, this is not the norm.

  13. I gladly volunteer myself for the cause. 
     
    To tell the truth, folk descriptions of admixtures here in Hawaii have gone back since it started happening a looooong time ago. Digging into old sociological and anthropological texts show that. 
     
    Agnostic: Razib is right. Anyone who has Hawaiian blood in them knows it. It’s too much of a bonus to not know it. It’s the difference in getting a free ride through college via private scholarships based on blood quantum or paying your own way. Official documentation here has listed racial admixtures in marraige and births going all the way back to the territorial period and geneology is a major hobby here. Also another thing is, Asian-Caucasian marraiges were extremely rare until the post-war period, long within the times of official documentation. 
    Granted, fudging does go on for various reasons.  
     
    My grandfather was listed as just Filipino in his birth certificate when he has enough Chinese in him to be mistaken as one.

  14. Chinese albinos have a pink tone to their skin. The subcutaneous fat doesn’t seem to make them look yellow. As to youthful appearance, that’s more likely a result of the skin being more elastic and less prone to wrinkling, also less susceptible to damage by exposure to sunlight. Chinese get much less skin cancer than people of European descent. 
     
    For what Razib wants to look for, I think one of the best places would be Macau – people of mixed Portuguese and Chinese ancestry who have been marrying each other for hundreds of years, with little history of other admixtures. The Maccanese are a phenotypically identifiable subgroup with their own culture and even their own distinctive cuisine.

  15. You might be right on that subcaneous fat issue. As far as cancer…I would say that on average Chinese are not as fair as Scandinavians, Slavs, or Celtic groups…they are more like Mediterranean Europeans or darker. The lightest people would be in the North, along with Koreans and Japanese. I have seen East Asians as light as a red head Irish person, but that is far from the norm. I also wonder do they tan darker, therefore burn less.

  16. I’m amused that in some places East Asians are counted as ‘white’. Chinese people don’t think they are white, they think Europeans are white and they are yellow. A common colloquial expression by Cantonese husbands for their wives is “yellow faced woman”. Not intended to be hugely flattering. Another one is “rice cooker”. Either one would get me a smack in the ear. 
     
    This is only anecdotal observation, but I think you can probably detect geographic trends in skin reflectance in China, both north-south and east-west. But it is difficult, because it is so dependant on individuals’ exposure to sunlight, mobility of regional groups within China, and a lot of natural variation within regional groups. Some Chinese people are naturally darker skinned, some tan very dark, some are very fair skinned and freckle, don’t tan much, and everything in between.  
     
    There are similar variations in Europeans – a lot of Scandinavians and Slavs tan more easily than say Scots and Irish. And Chinese generally are a lot more sensible about avoiding over-exposure, unlike my generation when I was a kid, pegged out on the beach for 3 hours every day in the summer holidays trying to barbecue ourselves. Some people even used to lie on a sheet of aluminium cooking foil to barbecue themselves more efficiently. Now we’re all trooping off to the skin specialist every year to get our solar keratoses removed. Notorious inherited Celtic susceptibility. I don’t know how the Scandinavians and Slavs score on skin cancer. 
     
    Koreans tend to be very light skinned. Japanese – varies, but a lot are very light skinned. But culturally, pale skin in women is so strongly preferred as ‘beautiful’ among these groups that there is a roaring pharmaceutical trade in ‘whitening creams’. No idea if they work. In Australia the pharmacies are full of artificial tanning stuff, in China and Japan they are full of whitening creams. It’s really quite funny, everyone trying to change colour, while continuing to use the same basis to discriminate against one another. Human beings are weird.

  17. Central Asia? Kazakhstan? Eastern Siberia and parts of Mongolia? A thousand years, or more, of intermarriage.

  18. I had the idea that there were TWO skin-coloring molecules: melanin which is brown and a second the color of a carrot. I’m Scots/Irish, a fair “strawberry-redhead” which means pale red, with pale freckles. But the carrot color means that I’m not the milky white of fairytale princesses — rather a kind of ivory. 
     
    In plants, I’m aware that there is a purple pigment in leaves as well as flowers — but is it ever in people? I’ve seen very dark black people with a blue-purple sheen — very striking. To my eye, Native Americans don’t look red but rather more like the lavendar of a Weimeraner dog, at least if they don’t work outside much.  
     
    It occurs to me that our skin-color categories are maybe too ideological to be strictly accurate. When one buys cosmetics, the categories tend to be poetic. What the heck color is “rachel,” anyway? (And who is she???!!) 
     
    Prairie Mary

  19. Mary, I think this explains pretty well what you are referring to: 
     
    http://www.cis.upenn.edu/~elli/tech-report.skin.pdf 
     
    Yes, people’s skin tone is not just a ‘colour’, it is a spectrum.

  20. Thanks, John. This is very helpful. I never thought about the use of skin color for identity verification. But I have thought a bit about the differences of skin color in terms of either indicators or causes of physiology. We know that one can’t tan without melanin, but I know people who say they can prevent sunburn by taking melanin orally. Also, there are studies that indicate that redheads metabolize pain-killers differently and even handle fluids either intra- or inter-cellularly in different ways. My dentist, a red-head, says that fair people are more prone to inflammation and swelling. 
     
    I wonder whether people with what I think of as a “blue” cast to their skin (aside from sufferers from anoxia) have even been studied. Native Americans are very wary about genetics and skin color, with good reason. 
     
    I’ve been thinking about this since a cosmetician custom-mixed a powder compact for me about sixty years ago. I noticed that one of her powder pigments was quite purple.  
     
    Prairie Mary

a