Actually, there are a lot of people with light skin today, since the population of China is still a way above one billion. But then, the fertility of the Chinese is almost as low as that of the Europeans.
It’s interesting that the genes responsible for the light skin of the Asian population, though, are different from the genes of the Europeans. I wonder if light skin originated separately in each population or if the initial genes responsible for light skin mutated over time in different directions. Or maybe the Europeans did get their white skin from the Neandertals and the Asians from the Denisovans or perhaps even from Homo erectus.
I believe skin color is a genetic response to differing levels of sunlight and environmental warmth. Even in Japan those whose ancestors lived in the northern islands have lighter skin than those who are from the southern ones.
Since there multiple genes responsible for skin color, it’s difficult to make assumptions based on one or a few of them.
Yes, Occam, that’s what is generally thought to have been the case. But I remember reading about some problems with this theory—I have been looking for it for a few days now and I can’t find it (I’ll keep looking). From what I remember the problem was related to the speed at which the mutations and adaptations would have had to take place—taking into consideration the fact that we left Africa around 70,000 years ago. The Neandertals and Denisovans would have had a lot more time to evolve lighter skin than us, and it is not therefore such a crazy idea to assume that perhaps the Europeans and Asians got it from them.
Yes, Occam, that’s what is generally thought to have been the case. But I remember reading about some problems with this theory—I have been looking for it for a few days now and I can’t find it (I’ll keep looking). From what I remember the problem was related to the speed at which the mutations and adaptations would have had to take place—taking into consideration the fact that we left Africa around 70,000 years ago. The Neandertals and Denisovans would have had a lot more time to evolve lighter skin than us, and it is not therefore such a crazy idea to assume that perhaps the Europeans and Asians got it from them.
Perhaps, but it is also possible that lighter skin evolved across a relatively small number of generations if Vitamin D deficiency became a severe disadvantage in survival to reproduction in dark skinned persons trying to survive and reproduce in northern climates.
Sure, Tim. That’s pretty much what Occam is saying and what is generally understood to be the reason why different skin tones exist: selection of skin colour has a lot to do with UV radiation levels. But!, it’s a bit more difficult to explain why, for example, Northern Europeans are much lighter than Asians who have lived in the same latitude. And there were other problems where, once again, I don’t remember the details well enough to be able to discuss now.
In this article, it is suggested that many new Guinea Natives have a “chunk” of Denisovan DNA. However, contemporary New Guinea natives are dark skinned.
Yeah, they don’t know if the Neandertal or Denisovan DNA is actually playing any major role in those of us who have it (I happen to have a quite significant chunk of the Neandertal DNA when compared to the average). But they are working on it!
Humans in colder areas who had lighter skin lost heat more slowly so had a survival advantage. Humans in warmer areas who had darker skin lost heat more efficiently (darker colors tend to radiate at a higher rate) and probably were protected to some extent from ultraviolet damage.
I haven’t heard that one before. Can you provide sources?
I thought the advantage of dark skin was UV protection while the advantage of light skin was to allow more light through for vitamin D production. But with technology and medicine these days, would these really be significant evolutionary pressures in the developed world?
EDIT: whoops, I see we’ve been over this. Must’ve missed those posts, sorry
Unlike the milk and coffee in your cappuccino, the genes in people don’t mix
Well, there’s genetic recombination. And I think there are multiple genes that contribute to the phenotype for skin color, and those can be mixed and matched. So they can mix like milk and coffee, but there is also a chance that they would not in each individual. But if skin color is indeed a significant evolutionary pressure in the modern world, then those who consistently have offspring that have an adaptive skin color will do best, and those mixes with lighter or darker skin would die out. Then you might say the mixing is “complete”
I imagine the strongest evolutionary pressure for ligter skin these days in our society is due to sexual selection. But, once again, since people with lighter skin have lower fertility than people with darker skin, this pressure is not evidently sufficient.
Sexual selection is actually a very tricky thing—if, indeed, it even exists. I have thought about sexual selection a lot, but I don’t think I am yet ready to discuss it. I find it really difficult to accept that animals will find a certain trait attractive just because they think it’s attractive. What would that even mean? If a certain phenotype is attractive because it promotes a higher fitness, then it’s not really due to sexual selection at all, but rather a result of the good old natural selection. If, OTOH, it does nothing (or very little) to result in higher fitness, then it leads to a maladaptation, as it takes the animal on the wrong track (i.e. “wrong” in evolutionary term). I am not a fan of sexual selection at all. I think Darwin got this one completely wrong.
