Gene Expression

Why it was best to be white

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Comments

  1. #1 saurabh
    April 28, 2008

    Err? Why the jump in Vitamin D production from the skin? Did the Sun suddenly get brighter?

    Also, I’m not sure how this relates to whiteness – after all the switch to an agrarian lifestyle covered pretty much the whole hemisphere. South Indians (for example) aren’t exactly white.

  2. #2 Mike Keesey
    April 28, 2008

    Err? Why the jump in Vitamin D production from the skin? Did the Sun suddenly get brighter?

    I think he’s referring to people getting whiter (in northern Eurasia, anyway).

  3. #3 Eric Lund
    April 28, 2008

    Why the jump in Vitamin D production from the skin?

    It wasn’t necessarily a jump in vitamin D production from the skin, but rather an increase in its importance. You’ll notice that farmers get less vitamin D from diet than do hunter-gatherers.

    Actually, that’s not the whole story. There is a subset of prehistoric farmers with a mutation that retards the development of lactose intolerance in adults. Their descendants are the peoples of western Asia, Europe, and northern Africa–the same areas where “white” people came from. These people got an extra boost because they still got some vitamin D in the diet.

    There is also a balance between vitamin D production from skin and susceptibility to sunburn. This is one reason why people from higher latitudes (e.g., Scandinavia vs. Italy, or China vs. Indonesia) tend to have lighter skin than those from further south.

  4. #4 ecoli
    April 28, 2008

    You can’t ignore the importance of location. You have a tradeoff between vitamin D production and UV radiation exposure from the sun. It pays to be white in europe, to maximize vitamin D production in a location with a higher angle of incidence, and less UV radiation.

    Similarly, Vitamin D deficiency is a common problem among dark-skinned peoples living in upper latitudes.

  5. #5 jim
    April 28, 2008

    I have a couple, quite possibly dumb questions. I’ll try to be brief. When and how quickly did whites evolve? (By white, I mean Caucasian.)

    Do we have rough dates for when the various racial and ethnic groups split off from each other? The other day there were stories claiming humanity was reduced to 2,000 individuals around 70,000 years ago.

    So 70k years ago all human beings on the planet would have looked roughly like sub-Saharan Africans? When did the first recognizably caucasian people develop? What did they look like? Did they look, say, Mediterranean?

    Is the idea that a tribe of African-looking humans started migrating north and, some # of years later (hundreds, thousands, tens of thousands?) their descendants looked recognizably Caucasian? How long did that transition take?

    thanks.

  6. #6 Sandgroper
    April 29, 2008

    That is what Razib is illustrating – that the Neolithic Revolution favoured selection for greater skin reflectance, to what extent depending on UV exposure.

    Define ‘recognizably Caucasian’.

    And you might want to note that at 70,000 years bp there could have been some population substructure within Africa.

  7. #7 Luis
    April 29, 2008

    Jim: we really don’t know for sure. In my not so humble opinion, the formation of the caucasoid type is part of the colonization of West Eurasia, though until the late UP (Magdalenian) we don’t really find skulls that are more or less the same as now. Earlier types (Co-Magnon, etc.) are surely related but more archaic (and somehwat distinct) in appearence (suff like very marked cheeks, much stronger jaws, overall more archaic look).

    As for pygmentation, I would think that blond hair may be older than other traits (and evolutionarily trivial), and could have been present since soon after the OOA event, as it’s not just found in West Eurasia but also in Australia and Melanesia. But the focus here is pale skin, that is not any absolute trait, but gradual and enviromentally modifiable (tanning). Some degree of pale skin could well have evolved in the UP, though, as noticed by the graph above, it was not such a dire evolutionary need as later in the Neolithic, specially among groups that practiced fishing (the main dietary source of vit. D). Apparently, recent genetic research suggests that the main change in this happened rather recently, in or near the Neolithic period, allowing possibly for the palest types among “whites”, who were best adapted to live in the darker conditions of Northern Europe and to need less dietary input of vit. D, even in such enviroment.

    Anyhow (and this goes for all), I am of the impression that the evolution of whiter types was probably gradual: first UP humans in Europe (at least non-Mediterranean Europe) would already benefit from such adaptation, then some more northern areas like Central but also Eastern Europe also give a plus to lighter skin, then, in the Epipaleolithic, when Northern Europe (properly speaking) begins to be colonized, the benefit is even greater, and finally Neolithic, with the alteration of diet, would give the final (and maybe decissive) impulse to this process, consolidating the dominance of “Nordic” (pygmentation-wise) types in Northern Europe specially, and of lighter (less brownish) types in the rest of West Eurasia and North Africa (and Central Asia before the Turkic migrations too).

    I’d like to discuss the known (or speculated) timing of the different pygmentation mutations, as I really think that the process was not sudden but gradual (step by step maybe). I suspect that you could surely speak of “white” West Eurasians already in the late UP, even if the “Nordic” (whitest) types were still undeveloped or rare.

  8. #8 toto
    April 29, 2008

    I interpret it like this:

    “Before the neolithic revolution, people ate more meat and fruits, had more exercise, and were less likely to get diseases, so they didn’t need as much skin-produced Vitamin D to boost their immune systems. After the Neolithic revolution, they ate grains, exercised less, and were more likely to get diseases, so there was a strong incentive to increase skin-produced Vitamin D levels, namely the aforementioned immune-system-boosting.”

    Of course, this leads to the obvious question: “is there a clear, well-established correlation in time between Neolithic transition and skin-whitening?”

  9. #9 agnostic
    April 29, 2008

    You left out the “appear exotic to dusky females” part…

  10. #10 Luis
    April 29, 2008

    Hmmm… vitamin D is not just to “boost the immune system”: it is essential for bone formation and its lack causes rickets and other health problems not directly related with the immune system. Also recenly Razib posted on some new research that strongly suggests that it’s most important in correct brain development. According to Wikipedia the main sources of vit. D in food are fatty fish and mushrooms, and to a lesser extent eggs. Ground meat and vegetables have negligible inputs of vitamin D, so unless hunter-gatherers in shadowy climates fished or gathered mushrooms frequently, or ate a lot of eggs, they were bound to have serious lack of this essential vitamin. So, almost necessarily, they should have started to evolve towards lighter skin (the only alternative source) early on as they moved away from the tropics.

    In fact it’s a “classical” rationale that East Asians are not as light pygmented as West Eurasians because they traditionally eat more fish, what may be correct or not, but sounds very persuasive in any case.

    Also I don’t think that farmers excercised much less than huntergatherers. They were more sedentary, of course, but they had to care their fields and animals almost every day too – and that’s a lot of excercise. What they may have experienced is a decrease of meat and fish in their diets.

  11. #11 Sandgroper
    April 29, 2008

    It’s also not true that East Asians are not as light pigmented as West Eurasians. The % of total visible light reflectance for northern East Asians is just as high as it is for northern Europeans assuming no tanning from UV exposure, but the reflected light is a spectrum of wavelengths, obviously, and the % of reflectance of different wavelengths varies between East Asians and Europeans, so that the perceived colour is somewhat different, maybe containing less pink and more yellowish tones, although it’s not a big difference. This is hardly surprising, given that pale skin in East Asians arose through a different genetic mutation than in Europeans.

    The fish story sounds very fishy.

    If you don’t believe me, refer to Elli Angelopoulou, who is not only the authority on the measurement of human skin colour, she’s also a hottie.

  12. #12 agnostic
    April 29, 2008

    refer to Elli Angelopoulou, who is not only the authority on the measurement of human skin colour, she’s also a hottie

    She’s pretty cute. Nice accent too.

  13. #13 razib
    April 29, 2008

    chill with the mayle gayze….

  14. #14 empiricus
    April 30, 2008

    Razib:

    I’m not sure how you are using “overall robusticity” in the tag cloud (i.e. much more robusticity among HGs than farmers). Do you mean developmental robusticity a la Waddington? That doesn’t seem to fit the context, so I assume you mean long bone (or cranial?) robusticity. But I don’t get the causal flow from robusticity of any type to the immune system. If you (or other commenter) would be so kind as to explain …

    Sorry for what I suspect may be a dumb question – I’m not as well read in the field as many/most of your readers.

  15. #15 razib
    May 1, 2008

    empiricus, farmers are whimpy. the term was kind of vague. perhaps i should leave it?

  16. #16 empiricus
    May 1, 2008

    Razib –

    OK, I assumed that you were using “robusticity” as a technical term rather than the general term “robustness”; the two are not synonyms AFAICT. Gotcha though.

    p.s. I like “mayle gayze”. Permission to use it, sir?

  17. #17 Luis
    May 1, 2008

    The fish story sounds very fishy.

    Ok. I take your explanation as much more plausible and scientific. I have indeed noticed that Mongols for instance are often quite pale and have rosy cheeks. But you also find very septentrional Siberians (I’m thinking in Nenets right now) who are rather light brown (“moreno”). So maybe there’s something in the fish after all (it is in fact the main dietary source of vit.D in any case).

  18. #18 Sandgroper
    May 2, 2008
  19. #19 Lyonside
    May 2, 2008

    There may be an increase in sunlight exposure due to deforestation, due to clearing land FOR farmland. After all, deforestation is blamed for causing in part the Little Ice Age in medieval Europe. It could easily explain an increase in exposure that provided some extra impetus to the dynamics already occurring.

    Also, as far as the human skin color spectrum goes, there’s light and then there’s PALE. Wasn’t there a study several years back essentially showing that the extreme paleness seen in some European peoples of Irish and Scandinavian descent (the type of skin color that never tans, just burns) is a fairly recent mutation, say 10K years or so? The gene was discovered by comparison to a similar gene in fish that did about the same thing. In my mother’s family alone (all Western European descent) there’s a huge spectrum of difference between my primarily Irish American grandfather (who burns and never tanned) and my primarily German-American grandmother (and aunt, and one uncle) who are undeniably “white”, but tan just beautifully.

  20. #20 razib
    May 3, 2008

    lyonside, search for “SLC24A5″ on this weblog.

  21. #21 Luis
    May 3, 2008

    Think ‘edible fungus’.

    Commercial producer does not mean raditional consumer. Russians are maybe among the most traditionaly attached to mushroom consumption and they don’t even appear on that map. Instead I doubt mushrooms have deep roots in US cuisine.

  22. #22 PhillyGuy
    May 3, 2008

    Just throwing this out there, but I wonder what other sort of adaptations besides pale skin and lactose tolerance Northern Europeans went through to cope with little UV exposure and a low vitamin-D cereal based diet? I remember reading in Evelyth and Tanner’s book, “Worldwide Variation in Human Growth,” that Northern Europeans show a delayed skeletal maturation compared to Southern Europeans as well as other races (Africans, Mongoloids, Indo-Mediterraneans, etc.). They noted that it was unlikely that this was totally environmental because in Australia children of Anglo-Celtic and other Northern European descent showed delayed skeletal maturation compared to the children of Southern European Immigrants that were born and raised in Australia. Perhaps a slower pattern of skeletal growth is another way to cope with low vitamin D diets.

    Perhaps this is at least a partial explanation for the height of the Dutch and other Northern European groups. Elsewhere in their book, Evelyth and Tanner note that people who undergo their pubertal growth spurt later tend to be taller and longer limbed than early maturers because they have more time to grow as children before their growth plates close. The longer limbs are due to the fact that the limbs grow much faster than the torso during prepubertal growth and that this then reverses during the pubertal growth spurt. They also noted, for example, that at any given sitting height East Asian young adults’ legs were about 4 cm shorter than their white counterparts’. They also write that while younger generations of East Asian children were about the same height as white children before puberty, their early maturation and growth spurt (about 1 year earlier) means that they are unlikely to reach a similar adult height as the white children. Perhaps this is part of the reason that Northern Europeans are taller than Southern Europeans and seem to have rather gangly, long-limbed physiques compared to, say, Southern Italians or Greeks, who seem to be rather stocky.

  23. #23 KC
    May 4, 2008

    See the Journal of Human Genetics 47:92-94 for an article on evolution of light skin color in European populations as distinct from those of East Asians–convergent evolution. Bear in mind that in this case the use of the terms European and East Asian refer to the CEPH-Diversity DNA panels used, not a racial category.

  24. #24 Sandgroper
    May 5, 2008

    Luis – I take your point, but East Asians are traditionally large consumers of mushrooms, and notably dried mushrooms (sun-drying is important). E.g. in north-eastern Chinese diets, mushrooms feature just about daily.

  25. #25 Luis
    May 5, 2008

    What you say, Philip Guy, makes a lot of sense to me. It’s long beeen noticed that people mature earlier (puberty for instance) in southern than in northern Europe and it may be largely genetic, even if it surely is also an adaptation to reduced vit.D input.

    Wonder if greater vit. D input (like in the US and Australia) may alter their biology one way or another.

    Anyhow, I would not use the word “stockier”, because many southern Europeans are slender, even if shorter in average, and many northern Europeans are very robust, even if taller. My only criticism anyhow. :)

  26. #26 Luis
    May 5, 2008

    Luis – I take your point, but East Asians are traditionally large consumers of mushrooms, and notably dried mushrooms (sun-drying is important). E.g. in north-eastern Chinese diets, mushrooms feature just about daily.

    Ok. I didn’t realize that you meant specificlaly China (the world’s largest exporter), sorry.

    I am anyhow under the impression that the culture of mushroom hunting, while extended, is much stronger and deeply rooted in the eastern part of Europe than in the West. It may be related to vit. D provisioning in high latitudes as well as to influences of Siberian shamanism.

  27. #27 Philly Guy
    May 6, 2008

    Luis,

    Here’s an example of what I meant by ‘stockiness’ of Southern vs. Northern Europeans. According to Cacciari et al, (2002), 20 year old males from N. and C. Italy are 1.77m tall and weigh 70.3 kg. Their S. Italian counterparts are 1.74 m and 73kg. Also, according to Fredriks et al (2003), 20 year old Turkish males born and raised in the Netherlands are 1.74m and 73.7kg. By contrast, according to Fredriks et al (2000), 20 year old ethnic Dutch males are 1.84cm and 73.7kg.

    I prefer to use weight (kg) divided by height (m) cubed rather than BMI because we are three-dimensional beings and the former gives an accurate idea of how people would look if you scaled them up or down without changing body proportions. By this measure, Dutch would be 11.8, N. Italians 12.7, Southern Italians 13.9. and Turks 14.0. In other words, if height was the same and these groups maintained the same proportionate breadth and depths of their frames relative to their heights, the Southern European populations would be much heavier.

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