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By Rick Weiss
Washington Post Staff Writer
Friday, December 16, 2005; Page A01

Scientists said yesterday that they have discovered a tiny genetic mutation that largely explains the first appearance of white skin in humans tens of thousands of years ago, a finding that helps solve one of biology's most enduring mysteries and illuminates one of humanity's greatest sources of strife.

The work suggests that the skin-whitening mutation occurred by chance in a single individual after the first human exodus from Africa, when all people were brown-skinned. That person's offspring apparently thrived as humans moved northward into what is now Europe, helping to give rise to the lightest of the world's races.

Leaders of the study, at Penn State University, warned against interpreting the finding as a discovery of "the race gene." Race is a vaguely defined biological, social and political concept, they noted, and skin color is only part of what race is -- and is not.

In fact, several scientists said, the new work shows just how small a biological difference is reflected by skin color. The newly found mutation involves a change of just one letter of DNA code out of the 3.1 billion letters in the human genome -- the complete instructions for making a human being.

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Read it here.

The problem is that this "like self" filter is probably not sufficiently generous enough to accommodate skin color very well. So family is obviously "like self", your immediate community is "like self", but less so, and so on. Then people of different color appear to be "not like self", and this was probably the first primitive basis for racism. The modern advancements on the subject simply attempt to put an intellectual veneer over what is fundamentally an instinct that should have been bred out of humanity tens of thousands of years ago.

I said it better over here, I think.

[ 16 December 2005: Message edited by: DrConway ]

White skin was more likely to survive to reproduction, in Eurasia, at some point in history. Whether that happened in Europe or further east is not clear. I know my ancestors (Hungarians) - nominally 'white' - migrated west from Asia about 1500 years ago). They weren't the first or the last wave of migrants from the East - who knows what they looked like when they came?

My theory, which is mine *ahem*, is that it's easier to locate skin parasites on light skin. The colder your environment is, the more this matters -- you live in dank furs and huddled in small spaces. That might give a slight physical edge.

But the main thing, as suggested above, is sexual selection. Light skin is a peacock tail.

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Light skin is a peacock tail.

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How do you figure that? I thought dark skin was the peacock tail.

Actually, I do think darker skin helps in the tropics. I spent time in Nicaragua and Colombia, and those with lighter skins appear to age more quickly.

I wonder about melanomas, too. My sense, based upon a few cases only, is that light-skinned people get them more easily in the tropics.

(That paler = better almost everywhere would be interesting, but it's too hard to filter out the unrelated status of Europeans after the Age of Discovery, since it's only from then we can have any real idea what was favoured in Africa or Americas. Asia, yes, but that's just 2 large samples.)

And you bet, the association of black with bad is just black with dark, which of course represents bad. No reason ever to say "black" with such a meaning; just substitute dark.

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Originally posted by DrConway:
I always wondered how this happened. It was my notion that somewhere along the line, the people who moved up north probably found their chances of success being like that of the polar bear's - that whiter skin tended to blend in better with snow and so the lighter extremes of the skin color spectrum tended to be reproductively favored.

A chance mutation probably accelerated this process though.

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I believe the selection pressure mostly had to do with rickets. Skin with less melanin blocks less sun from lower layers of skin making with the vitamin D, or something. If you're in latitudes where the sun's wimpy enough that light skin doesn't cause mucho sunburn problems etc., then it's a net benefit.
I suspect that in Northern Europe, even stone age folks wore clothes of some sort, so camouflage wouldn't be all that big an issue.

I don't buy the peacock tail thing. Selection pressures don't need to be that big to have a major cumulative effect, and at the same time it seems pretty clear that as soon as differing populations start to mix, they get together and have kids, so I don't see how sexual selection is supposed to work.
I think people are underestimating the difficulties of life back when. Somewhat less vitamin deficiency could certainly make the difference between surviving the winter and not surviving the winter.
On the other end, you don't even need skin cancer to explain selection pressures. Just at the simple level of vulnerability to bad sunburn and heatstroke, if you have no choice but to keep on gathering or hunting until you're ready to drop, then the light skinned person is either ready to drop quicker (and hence gets less food) or, if they insist on being stubborn about it because starvation's staring them in the face, may simply drop dead. My wife nearly died of sunburn and heat stroke one time in *Vancouver* when she was a teenager. I'm sure it can't be that tough to do so in many parts of Africa.

[ 18 December 2005: Message edited by: Rufus Polson ]

Edited: (RP beat me to it)

[ 18 December 2005: Message edited by: Serendipity ]

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Originally posted by CHCMD:
Is it just human males that have nipples? I was wondering about that 'cause my male Beagle doesn't have any nipples

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I remember R.L. Jr suggesting that at one time, Northern Europe and Scandinavia were likely much warmer and sunnier than now. Our black ancestors likely figured out big game migratory patterns and followed herds northward. And small groups settled north for the longrun as lost ties with the south in favour of an abundance of meat. There would have been feasts and famines, malnutrition etc with some hair colours turning red. African children's hair will often turn red when suffering from qwashiorker stage of malnutrition. It produced a more robust group of Nordics who are thought to have mixed with earlier Innuits and relatively recently?, Swedish wikings mixing with Mongols and Steppe people with the result - Russians.

Which does bring up the problem of European hair: in all the world, Europeans are the only types with a variety of hair colour. (Not counting albinism, but noting the occasional blond Melanesian.) Why on earth is that?

Spelling!

[ 21 December 2005: Message edited by: Southlander ]

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Originally posted by Boarsbreath:

Which does bring up the problem of European hair: in all the world, Europeans are the only types with a variety of hair colour. (Not counting albinism, but noting the occasional blond Melanesian.) Why on earth is that?

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There are polygenic models for blonde hair, apparently, but no one has actually been able to gene type the encoding for blonde hair - typing exists for red and brown, according to something I read. (Don't call me on it bc I enjoy a superficial understanding of this subject in vague generalities)

This person discusses a possible explanation for red hair. Is it because there was no selection against gene mutations for red hair among northern Celtic tribes ?. (But I thought Celts extended from India to Mediterannean(including Italy and Spain) N Africa and British Isles?)

[ 22 December 2005: Message edited by: Fidel ]