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[QUOTE]Originally posted by Bob_01: [QB] [QUOTE]Originally posted by Chimu: [qb] Yawn, your reposting of earlier quotes does not change the fact that you have no direct evidence (as in an actual genetic explanation) that would indicate that one was definitely the derived version and the other the ancestral version. [QUOTE]Originally posted by Chimu: [qb] [QUOTE]Originally posted by The Explorer: [qb] Your opinionating that the Bisa Sandawe are "lighter" in no way changes the fact of the study that you are citing above about dark skin alleles in Africans and Melanesians, nor does your *personal* characterization of the Sandawe as "lighter" make them not to be "dark" complexioned folks, that is to say, "black".[/qb] [/QUOTE][IMG]http://i49.tinypic.com/142eiqe.jpg[/IMG] And this is an orthochromatic picture for sure, so the older guy could be even lighter. But you still see the difference. [QUOTE]And indeed, they'd have to have ancestral alleles, because after all, that is what's keeping them "dark complexioned". In the meantime,... [i]The [b]lightly pigmented[/b] hunter-gatherer San populations of Southern Africa is exceptional in having a [b]high frequency[/b] of the [b]derived allele[/b] relative to geographically proximate and more darkly pigmented African populations (Jablonski and Chaplin 2000), further supporting the importance of OCA2 in regulating normal variation in pigmentation. The widespread distribution of the derived allele in the CEPH-Diversity Panel suggests that it is not necessarily a new mutation, nor has it been restricted to a specific geographic area.[/i] - Norton et al. Note that while it is said that the allele in question is suggestive of not being a new one, it is recognized as being in the "derived" state. [/QUOTE]Sorry but no can do. [QUOTE]From: Heather Norton To: Jaime Andres Pretell Sent: Friday, February 27, 2009 4:29 PM Subject: Re: Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians Dear Mr. Pretell, Thanks for your interest in my work. Yes, these genes "exist" in other primates. That is to say, primates have stretches of DNA sequence that produce the same protein in humans and in chimps, and these are usually found in the same corresponding region on their chromosomes. So, it would be correct to say that both humans and chimps, for example, have the gene for ASIP, OCA2, MC1R, etc. When we look at the sequence of individual nucleotides (A, C, G, or T) that make up a particular gene, we may see small differences between chimps and humans. So, for example, at one place in the OCA2 gene chimps might all have a "G" base, where humans all carry an "A" in the corresponding position. This is what is known as a fixed difference, and studying fixed differences may help us to understand why humans and chimps differ for certain traits. However, you can imagine that there may be other cases were chimps carry a "G" at a certain position while some humans carry the "G" and others carry an "A". When we see the same nucleotide being carried in both species (in this case, the "G") we call it the ancestral allele. When the nucleotide differs (in this case, the "A") we refer to it as the derived allele. The term allele here is used to refer to a different versions of the same gene. So, while chimps and humans have the same pigmentation genes (so do mice, and pigs, and fish), they may carry slightly different versions of that gene. Sometimes we see slightly different versions of a gene within the same species. These different versions may explain some of the physical differences (like skin pigmentation) that we see among individuals. In other cases, though, these differences don't affect the protein that the gene produces, and so they don't seem to explain physical differences. The question of the San and Sandawe is an interesting one. [b]We are not sure if the alleles that explain why their pigmentation is so different from neighboring populations reflect new (derived) mutations or if instead maybe they are actually ancestral alleles shared with light-skinned primates.[/b] I would say that this is an area of open investigation. As for ASIP and OCA2...I think that even if you ignored the contribution of these two genes to pigmentation variation we would still see good range of diversity. For example, genes like SLC24A5 and MATP also have a major impact on phenotype. I would also assume that in the past there was variation in human skin color. It would be unlikely to be as much variation as we see across the human species today, since today modern humans live in a range of environments where different pigmentation types are more or less adaptive. In general, I would say that the pigmentation of early humans, who originated in Africa, was dark to provide protection against the damage that ultraviolet radiation can do. However, when we look at populations in Africa today (or populations living in other places where ultraviolet radiation is strong) we see a wide range of variation in pigmentation--I suspect that if we could go back in time we would probably see similar levels of diversity to those that we see in Africa today. Thanks again for your interest--if you have any more questions, please let me know. Cheers, ~Heather [/QUOTE]Again. Bisa Sandawe lighter than Bantu, and no evidence that it is the derived gene. Norton clearly says that while, like Jabonski, she beleives that the environment will favor darker skin, the genetic allow for the full diversity from the get go, and history has shown us that lighter (as in San and Bisa Sandawe lighter) populations have existed from South Africa all the way to Tanzania. Area for open investigation. [/qb][/QUOTE][/qb][/QUOTE]Do you have any paper regarding melanin level suggesting that? Just because someone (whoever they are) may observe that doesn't mean it's true. [/QB][/QUOTE]
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