I just don’t get it. Does having light skin in Europe really have enough of a survivability advantage to make whites white? What’s the story? Is it genetic drift? Why do we have the main races? Is the change smooth from Ethiopia to Eastern China and from Ethiopia to Scandinavia and from Scandinavia to Eastern China? Does anybody really have a good empirically verified answer, or is it all speculation? What’s the straight dope?
I don’t have the hang of effective SDMB searching yet, I’m sure this must have been covered. Please forgive me if it has.
This goes beyond my knowledge of anthropology, but I do know it hinges on vitamin D, to a point at least. Darker the skin, the more sun you need to get it and vice-versa. So Europeans are pasty so they can get less sun but still produce enough vitamin D. Also black skin is more immune to skin cancer, can stand more sun. So that balance probably plays a part.
What’s also always been curious to me is why Asians have the extra skin flap which form their almond shaped eyes. I’d assume Cecil has covered this at some point though, hopefully someone who knows their way around better than I will link us to an article soon.
For the second of my two cents, I’d also be pretty confident in saying the main races have formed due to the pattern of world colonization leading out of Africa: civilizations are started up far away from home and the local enviroment shapes the people there. Since a relatively small number of large geographical areas served as starting points of civilizations, the local enviroment acted upon the people in each to shape them into what we have today, roughly. There is very solid evidence for this, but I wouldn’t be able to cite it off hand.
as far as separate races is concerned…that’s a debate in itself.
It is becoming more widely accepted that there is only ONE race and that there are three to six separate groups/populations within OUR race that are distinct from one another.
Will these distinctions continue to exist? Good question. If evolution relied on only natural selection I would say more than likely. Today the “races” are no longer isolated as they once were. People of different cultures are marrying one another. Their children, and so on. Less people can claim to be descended from a single culture/race/nationality each year than the one before, despite the increase in population.
Add to this “blending” of the human race the fact that some genes which determine traits/features are dominant, it is simply a matter of time before ALL mankind will become a single race again. I say again because it is commonly accepted that we all originated as a single race. Not black or white…brown w’ varying shades.
In response to the genetics, IIRC there are 6 genes responsible for skin color. A combination of these 6 lead to really white skin all the way to pure black.
As for the question regarding smoothness of change, I once had a photocollage of indegenous people from all over the world, arranged in a pattern similar to that found on a world map.
Wherever there was a current or former land path, change was invariably gradual and slight.
“Races” as they are commonly used are merely social fictions.
People who the direct ancestors of today’s “white ethnics” did not suddenly show up in northern Europe and turn white. They migrated there from the Middle East or Caucasus Mountain (yes, the origin of Caucasian) areas (depending on which theory you accept) several thousand years ago. Those peoples were already a lighter skin color than those who lived in central Africa.
People in the north of Europe did not have good sources of calcium. Sunlight falling on exposed skin will create vitamin D which aids in the digestion of calcium, but they received smaller amounts of vitamin D from the sun than Africans. Less melanin blocked less uv in sunlight.
This is an older notion and has received some criticism in the academic press. Other factors are now thought to be involved. One interesting one is that being able to digest lactose helps to digest calcium. Those with the mutation that allowed for milk drinking as adults had a natural selection advantage over those who didn’t. This helped spread lactose tolerance though white northern Europeans. The late anthropologist Marvin Harris wrote on this in several of his books.
Races are not entirely social fictions, I wish I had the cite but I’ve recently read that there are concrete genetic differences between the races, at least according to forensic experts. And anyone know why Asians have the skin flap that gives their eyes the almond shape? Random mutation? Keep out the sand?
Saying that there are three to six separate populations within humanity is equivalent to saying that there are three to six races. But it was my impression that, to construct any sort of biologically significant subcategorization, you needed hundreds or more different populations.
You might hold off believing it, just yet. Note that the author of that claim is J. P. Rushton and he provides no evidence to support his claim. On the other hand, in the same link, Scott MacEachern points out that there is no solid evidence that East Asians “evolved” in colder climes and that a substantial portion of the range of people with epicanthic folds is in tropical regions.
I am not sure what the prevailing theories regarding epicanthic folds are, but I would not take this single, unsupported throw-away line as indicative of the best guess that paleo-anthropologists have on the subject.
(As an example of Rushton’s haste, it should be noted that the African Khoi-San–living in deserts and sub-tropical climates–also have epicanthic folds. An adaptation against sun glare seems possible, given the proximity of the Khoi-San to the Kalahari desert, but I would still do some exploring before I took that as a given, as well.)
And where does one definitively draw the line among these “races”? If no line can be definitively drawn, then how hard-and-fast are these “races” and how much social policy really should be based on these “races”?