Not all genes are equal in the eyes of man

By Razib Khan | September 13, 2010 12:19 am

Kalashpeople_20100312A few days ago I was listening to an interview with a reporter who was kidnapped in the tribal areas of Pakistan (he eventually escaped). Because he was a Westerner he mentioned offhand that to “pass” as a native for his own safety he had his guides claim he was Nuristani when inquiries were made. The Nuristanis are an isolated group in Afghanistan notable for having relatively fair features. His giveaway to his eventual captors was that his accent was clearly not Nuristani, and master logicians that the Taliban are, the inference was made that he was likely a European pretending to be Nuristani.

I thought about this incident when looking over the supplements yesterday of Reconstructing Indian population history. On page 19 note S2 figure 1 includes the Kalash of Pakistan. These are the unconverted cousins of the Nuristanis who were not forcibly brought into the religion of peace in the late 1800s because their region of the Hindu Kush was under British rule, who naturally imposed their late 19th century European value that populations should not be converted by force to a particular religion (Nuristan means “land of light,” whereas before Afghans called it Kafiristan, “land of the unbelievers”). Despite the fair features of the Kalash, which has given rise to rumors that they are the descendants of Alexander the Great’s soldiers, they cluster with Central and South Asian populations, not Europeans. Like the Ainu of Japan it seems superficial similarities to Europeans, at least in relation to the majority population around them, has resulted in an inordinate expectation of total genome exoticism, when in reality a few particular loci are producing the distinctiveness.

Figure 1 from the 2007 paper, Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians, brings home the point:


skinfig1

The first panel shows a representation of the genetic distance across the genome. Or at least enough to give you a good sense of the phylogenetic relationships. South Asians and Europeans form a clade, as do Native Americans and East Asians. The subsequent panels show Fst values, between population variance, on five genes known at that time to be implicated in between population skin color differences. Note now much different the trees are from the one generated by a large number of loci. Since then more loci have come out of the woodwork, and the peculiar genetic architecture of pigmentation has been rather well characterized. Though most genetic variance may be found within continental races, pigmentation is quite often the exception to this rule. Most of the variance on these loci can be between the races. On SLC24A5 West Africans and Europeans have nearly 100% between population variance. The allele frequencies are disjoint. This shouldn’t be that surprising, skin color is highly heritable, and we already know that there’s a lot of between population difference. So from that one would infer that there would be a lot of genetic variation.

Our skin is our largest organ, and is extremely important as a visual marker of health, age, and identity. The fact that there is so much salient interpopulation difference matters a great deal in the “folk taxonomy” of our species. When considering the relevance of skin color in our taxonomies I thought back to Jared Diamond’s 1994 piece for Discover, Race Without Color:

Regarding hierarchy, traditional classifications that emphasize skin color face unresolvable ambiguities. Anthropology textbooks often recognize five major races: “whites,” “African blacks,” “Mongoloids,” “aboriginal Australians,” and “Khoisans,” each in turn divided into various numbers of sub-races. But there is no agreement on the number and delineation of the sub-races, or even of the major races. Are all five of the major races equally distinctive? Are Nigerians really less different from Xhosas than aboriginal Australians are from both? Should we recognize 3 or 15 sub-races of Mongoloids? These questions have remained unresolved because skin color and other traditional racial criteria are difficult to formulate mathematically.

16 years on I think we can reasonably answer many of Diamond’s questions with phylogenetic trees such as the one to the left. There are five races in the tree by coincidence, though the Khoisans are with Africans, and the Americas has its own branch. Yes, Nigerians are probably less different from the Xhosas than Aboriginal Australians. And I guess this tree implies closer to 15 “subraces” for “Mongoloids.” And with the rise of skin reflectance measures the trait isn’t that difficult to formulate mathematically actually.

But as for the salient phenotypic characteristics which humans use to classify each other, and which will remain important socially and culturally for the near future, it makes absolutely no sense to minimize the critical importance of skin pigmentation. Humans are a very visual species, and the complexion of our largest organ will always be of particular interest. This sort of phenetic classification is not scientifically rigorous, I don’t want cladists to hunt me down, but, it is not an arbitrary cultural construct. We can’t classify people by HLA profiles because we don’t have conscious access to such information (and the idea that we can “smell” HLA profiles is still unproven). Our innate pattern recognition competencies are such that naturally folk taxonomies will start with complexion, and use other characters to refine our categories. Just because something isn’t scientific doesn’t always mean it’s silly or arbitrary.

Image Credit: Outlook India

Addendum: I just realized that Jared Diamond’s article came out at the same time as The History and Geography of Human Genes. A quick consultation of this seminal work would have cleared up some of his questions.

CATEGORIZED UNDER: Anthroplogy, Genetics
  • Pingback: Tweets that mention Not all genes are equal in the eyes of man | Gene Expression | Discover Magazine -- Topsy.com

  • bioIgnoramus

    Given that it is apparently simple for Man to evolve as, at the extremes, black or white, it’s odd that we don’t have a zebra-like race.

  • bioIgnoramus

    Oh well, I make my rather feeble joke and then later the same day stumble across this.
    http://www.dailymail.co.uk/news/article-1311533/Black-white-twins-Sisters-Marcia-Millie-Biggs-set-day-school.html

  • onur

    All those examples are from fraternal (non-identical) twins, so there is nothing abnormal.

    No need to say that those twins have nothing to do with a zebra-like or a Tenctonese-like race. :)

  • DuncanH

    Can you shed some light on this sentence from Wikipedia: ” In one cluster analysis with (K = 7), the Kalash formed one cluster, the others being Africans, Europeans/Middle Easterners/South Asians, East Asians, Melanesians, and Native Americans. ”
    http://en.wikipedia.org/wiki/Kalash

    Does this mean the Kalash are a race as distinct as the other races listed?

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    Does this mean the Kalash are a race as distinct as the other races listed?

    it means that if each K is a distinct “race” :-) the kalash are a very distinctive population which probably has been isolated for a long time, probably because no muslims came into their region. you could find plenty of other very distinct groups.

    in short, i’d say no. i think it is probably not good to live & die by K’s alone from structure when you have nothing else to go on.

  • onur

    As far as I know, the Kalash cluster only showed up in early autosomal studies like Rosenberg et al.’s studies (and only in Rosenberg et al.’s studies if I am not mistaken).

  • http://www.kinshipstudies.org German Dziebel

    “But as for the salient phenotypic characteristics which humans use to classify each other, and which will remain important socially and culturally for the near future, it makes absolutely no sense to minimize the critical importance of skin pigmentation. Humans are a very visual species, and the complexion of our largest organ will always be of particular interest.”

    In addition to adaptation, sexual selection may have influenced the distribution of skin colors around the globe (see the works of Manning and Frost). Europeans are very light in conjunction with long-term high rates of monogamy, while Africans are very black in conjunction with long-term high rates of polygyny (African foragers are lighter than African agriculturalists, and the rates of polygyny are much higher in the latter). This explains why Europeans and Africans are so widely divergent in the trees above – they diverged into polar extremes from a more neutral prototype. It’s precisely these extremes of skin pigmentation – white and black – that are at the root of modern pre-occupation with race. If it weren’t for blacks and whites, no race issue would’ve existed. If sexual selection played a role, then these radical differences aren’t just products of nature, which we need to pay behavioral respect for, but products of past human behavior as well, hence subject to human control in the future.

  • onur

    It’s precisely these extremes of skin pigmentation – white and black – that are at the root of modern pre-occupation with race. If it weren’t for blacks and whites, no race issue would’ve existed.

    Cannot agree with these. Races weren’t primarily defined only based on pigmentation, but also features of the skull, especially facial features.

  • http://www.kinshipstudies.org German Dziebel

    “Races weren’t primarily defined only based on pigmentation, but also features of the skull, especially facial features.”

    Sure. But it’s only because of the skin color that the race discourse propagated so easily in the public sphere. Even in a most politically correct environment we’re allowed to say “blacks” and “whites.” Skin color leads the race conversation. Without these marked differences, the race issue would’ve stayed within a narrow group of human diversity connoisseurs. And it’s precisely the extreme values of this key racial attribute that are likely sexual-selection driven in Europe and Africa.

  • bioIgnoramus

    “Skin color leads the race conversation.” Perhaps in the US it does, but elsewhere? Always? If there had been a Google 100 years ago, would it have found that disobliging references to Chinamen in California would have referred more to their skin colour or to their eye-folds? Or even to their habits?

  • onur

    German, brunette Caucasoids of South Europe and the Middle East distinguish Mongoloids, who are mostly brunette, from themselves based on not pigmentation but facial features, and they clearly see Mongoloids as the Other.

  • http://www.kinshipstudies.org German Dziebel

    Onur, it’s splitting hairs now. Of course, people notice phenotypic differences around them, but neither the eyefold, nor facial flatness is as salient and instant as skin color.

    Bioignoramus, I don’t know what would have happened if Google was invented 100 years ago, but the U.S. is the arena in which the relative perceptual salience of different phenotypes has played out. Prior to the settlement of the Americas, the extremes of human phenotypic variation didn’t mingle so freely together for such as long period of time.

  • onur

    Onur, it’s splitting hairs now. Of course, people notice phenotypic differences around them, but neither the eyefold, nor facial flatness is as salient and instant as skin color.

    If every race had similar pigmentation averages and ranges, then facial features would be more salient than today and would be the sole primary criterion in classifying races, or at least primary races. So races would certainly still exist, and with them, race talk, and not just among a small group of professionals, but very widespread: down to the lowest levels of the societies.

  • http://www.kinshipstudies.org German Dziebel

    “If every race had similar pigmentation averages and ranges, then facial features would be more salient than today and would be the sole primary criterion in classifying races, or at least primary races.”

    Okay, I got it. Yes, it’s possible. Theoretically. My point was, though, that, in practice, the fact that there are two polar opposites in the skin color variation, namely Blacks and Whites, was conditioned by sociocultural factors (in addition to natural factors), and it’s precisely those two sexual-selection driven racial characteristics that achieve such a salience in the public eye. Could you give an example of a hypothesis that ties eyefolds or other visible racial markers to sexual selection or other behavioral adaptations?

  • onur

    German, you set out from two assumptions or hypotheses: 1) Extreme skin colors in Caucasoids and Negroids are both results of sexual selection 2) Only sexually selected traits lead to widespread pre-occupation with race.

    And now you request me to join you in your hypothetical world. Sorry, but I have more important things to do.

  • http://www.kinshipstudies.org German Dziebel

    Onur, a hypothesis is a first step toward a scientific understanding of the world. I quoted the sexual selection hypothesis which goes all the way to Darwin. Most recently it was explored by Manning and Frost (see, e.g.., Frost, P. (2008). Sexual selection and human geographic variation, Special Issue: Proceedings of the ND Annual Meeting of the Northeastern Evolutionary Psychology Society. Journal of Social, Evolutionary, and Cultural Psychology, 2(4), pp. 169-191). You can download it from the web. The special salience of skin color in racial discourses is a pretty obvious one, and Razib mentioned this fact in his post. If skin color is the only racial attribute that will end up proven to be driven by sexual selection, then we’ll have a nice correlation to work with. You can falsify it by showing that other racial attributes that have been argued to be based, at least in part on sexual selection, are also prominent in race talk. Or you can falsify it by showing that race is a cultural construct that preys on any physical attributes just for the sake of perpetuating itself.

    You haven’t done either. And if you prefer to spend your time not on hypotheses and theories but on dogmas and speculations, you’re most welcome to do so.

  • onur

    German, I am already aware of Peter Frost’s hypothesis. His hypothesis has nothing to do with your contention that there wouldn’t be widepread race talk if such extreme pigmentation differences hadn’t evolved in humans, and he says nothing about that. He also neither claims that only sexually selected traits lead to widespread pre-occupation with race nor says anything about whether race-specific facial features (except those about pigmentation) were sexually selected or not. Your overemphasis on White-Black skin color differences to the disadvantage of all other SALIENT racial differences is a completely artificial and a too US-centric attitude.

    What I have written in this thread isn’t dogma or speculation, but expressions of knowledge and observations about various human societies worldwide (not just the US) and also logic.

  • toto

    If it weren’t for blacks and whites, no race issue would’ve existed.

    Go tell Pygmies or Samis that they never suffered racial discrimination from similarly-coloured groups.

    Nuristan means “land of light,” whereas before Afghans called it Kafiristan, “land of the unbelievers”

    FWIW, even non-Afghan Pakistanis still casually call it “Kafiristan” in everyday conversation.

  • onur

    What I have written in this thread isn’t dogma or speculation, but expressions of knowledge and observations about various human societies worldwide (not just the US) and also logic.

    and also knowledge about the history of racial classifications

  • http://www.kinshipstudies.org German Dziebel

    “Go tell Pygmies or Samis that they never suffered racial discrimination from similarly-coloured groups.”

    Height (in the case of Pygmies) is indeed another interesting example. It’s instantly visible and can outweigh other phenotypic attributes. However, skin color still looks like a greater divider than height. African Pygmies in the U.S. will be classified with “blacks” and not with midgets. Also, Pygmies and Saamis are not “races.” Discrimination, of course, can take different forms.

    “German, I am already aware of Peter Frost’s hypothesis. His hypothesis has nothing to do with your contention that there wouldn’t be widespread race talk if such extreme pigmentation differences hadn’t evolved in humans, and he says nothing about that.”

    I never claimed he did. I said that I married his (and Manning’s – read him, too) hypothesis of sexual selection affecting skin pigmentation and manifesting itself in some very specific and quantifiable behaviors (e.g., polygyny) and the idea that the extremes of skin pigmentation are at the center of public race talk.

    “Your overemphasis on White-Black skin color differences to the disadvantage of all other SALIENT racial differences is a completely artificial and a too US-centric attitude.”

    There’s nothing artificial about it: only in the U.S. the extremely black populations from West Africa (the intrinsic part of the agricultural, highly polygynous belt in Africa) co-exist with extremely white (practicing long-term monogamy, as Manning noticed) populations from (dominantly northern and central) Europe. And the racial tensions along the black-white divide are unparalleled. Russia, on the contrary, is the country with extreme differences in the strength of an eyefold, but the “tensions” between Caucasoid Russians and Mongoloid populations in Siberia or the Caspian Sea (the Kalmyks) are nowhere near those between whites and blacks in the U.S. In racial slur, of course, there are references to “narrow-eyed people” but it’s never part of common parlance.

    I’m aware that other factors such as local political and economic organization play their part in offsetting the direct cognitive impact of phenotypic differences but I do believe that most salient, long-term and geographically wide-spread phenotypic differences (such as skin color) are not purely natural adaptations. This is further connected to my larger thinking that, say, American Indians are not as black as Sub-Saharan Africans not because they are new comers to the New World but because the rate of polygyny is much lower there than in Africa. And Sub-Saharan Africans are as black as they are not because they’ve lived under UV light longer than any other human population but because the darkest of them show world highest polygyny rates (with the UV light component affecting all equatorial populations similarly). But this is beyond the scope of this string.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    onur, i’m sorry, i mistakenly deleted your last comment! can’t seem to find where the “trash” bin in WP is.

  • onur

    Do I have to rewrite it from the beginning or instead should I wait for you to restore the deleted comment?

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    you’ll have to rewrite…i don’t have access to discover’s wordpress ‘trash’ bin because of constrained settings. i could email admin, but it will take at least a day for them to get it back as it’s after office hours.

  • onur

    Well, I can wait then, as I am not good at rewrites; everything is better in the original. :)

  • onur

    Razib, any news from my deleted comment?

  • onur

    Razib, I asked you a simple question.

  • onur

    Razib, if there is no hope for my deleted comment, please inform me of it.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »