Tuesday, February 13, 2007

It's good to be black...and white   posted by Razib @ 2/13/2007 06:34:00 PM

This story, China's changing skin colour caught my attention. The relevant points:
"Traditionally, the first objective of a woman is to have pale white skin because whitening can cover many flaws. Many Chinese women will put on sun protection just to go next door because they're so afraid of getting any kind of sun rays," he added.
Dark skin in Imperial times was associated with labouring in the fields.
But for a growing number of young Chinese people, dark skin now means having the money to afford foreign holidays or Western-style glamour.
And a deep dark tan would appear to be one of the easiest ways to show that you are basking in China's new-found wealth.

Of course, "dark" is relative, just as "light" is relative. The article is a bit impressionistic for my taste, but, let's assume that it is suggestive of a counter-trend to the historical norm (I know there is a hip-hop counterculture among Japanese youth where tanning is fashionable). There are two issues:

1) International models, or at least non-local models, have influence. Before the rise of European hegemony in places like Japan black hair and epicanthic eye folds were considered beautiful. Today hair lightening and eye surgery are common in the Far East.

2) Within society mores (partly driven by emulation of global standards) where the transition to factory work has resulted in an urban proletariat that is indoors most of the time and a professional class which has time for "sun and fun" trips abroad.

Obviously this is more complicated than "darker = affluent," as a dark skinned South Asian or Africans are obviously not dark because of their trips abroad, so I doubt they would be the objects of any assumptions about their disposable income or usage of leisure. Nevertheless, I do think that it is interesting that the same cultural shift affected much of the Western world in the early 20th century, as the association of white skin with aristocratic shielding from outdoor labor became confounded by the fact much of labor now occurred indoors and so resulted in light skin. One can see similar shifts in other areas, in the United States obesity has a low SES implication, while a fit and trim look suggests someone who can afford high quality but low fat food and possible items such as a gym membership. This is obviously a shift from the previous norm, still found in many cultures where the median caloric intake is far lower (the rise in obesity in India and China is a phenomenon of the upper classes from what I know).

But now I want to focus on the past, and the emergence of light skin. I've talked about the genetics of skin color a fair amount, but an interesting point is that some loci, such as MC1R in East Asians and OCA2 Europeans (OCA2 is the major loci which controls blue eyes vs. non in Europeans, but it has some affect on skin color as well) have been under recent positive selection, within in the last 10,000 years. What's going on here?

I'll offer a tentative hypothesis, though I don't assume this is a sufficient condition: agriculture resulted in far greater social stratification was possible before as small hyper-fertile elites emerged. These elites did not engage in farming as a day to day activity (they might have been males warriors and their households), and so were environmentally lighter skinned. Additionally, hypergamy existed in these communities whereby high status males would engage in polygyny and selected the "fairest" females from the population. The elites were self-conscious about their light skins, and so the beauty norms shifted toward this model. Within the general populations there was some heritable variation in skin color, and those women who were genetically lighter skinned were socially promoted far more often than those who were not into the harems of elite men. These men had offspring who tended to become genetically lighter skinned. This process would repeat every generation, and as the elite always repopulated lower classes (perhaps the elite had secure grain stores that they monopolized that allowed them to survive famines) the light skin kept percolating down from on high. So the parameters I am suggesting are:

1) Greatly increased male reproductive skew, with a strong correlation between fitness and high status, caused by the onset of agriculture.

2) Hypergamy of genetically light skinned females into the elite, resulting in a correlation between light skin and high status which had genetic, as well as environmental, roots. Of course, lighter skinned women would also be fitter than darker skinned women simply because presumably their mates would be better providers.

Of course, I suspect there was some tendency to prefer lighter skinned females naturally because of its correlation within a population with youth and fertility (women get darker with successive pregnancies and after puberty). And, I think there might be other selective factors at work. But this is a start.

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