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[QUOTE]Originally posted by MindoverMatter718: [QB] Might as well add mine from the other thread... Chimu, in equatorial East Africa, where modern humans evolved, where dark skinned populations are seen in today's tropical East Africa, is how dark modern humans who left Africa were. This is all you have to worry about. That single population who left Africa. Not the San in South Africa or any other African population. Ancestors of modern humans migrated from equatorial East Africa, not South Africa, so the complexion of the San has nothing to do with the original humans who left Africa to become non Africans who were indeed dark skinned as today's equatorial East Africans. Lighterskin is needed when humans moved into northern Latitudes, since ligterskin allows for synthesis of UV to produce Vitamin D, under darker skies. Pale skin is best explained through the spread of farming, There are two general sources for vitamin D—sunlight and diet. We know that a farmer’s diet does not have enough vitamin D, meaning that people in farming-based societies need to get a lot of it from the sun. We also know there is not enough sunlight in Northern Europe for dark skinned people to get enough vitamin D. So farming based societies that live in Northern Europe need to have lighter skin. But farming didn’t really take a hold in Europe until 6,000 or 8,000 years ago. So what about the 30,000 or 35,000 years that people lived in Europe before farming you ask? Well, If there was enough vitamin D in their diet, then there would have been no need for pale skin. Recent genetic work suggests that the diet of these hunter-gatherers had plenty of vitamin D. Therefore humans in Europe were therefore brown-skinned for 10's of thousands of years before they turned pale. The convergent evolution of pale skin in Europeans and East Asians, was completely independent of Africans and of each other, so even if Asians became lighter around 15ky before humans in Europe, this would have no bearing on Europeans at all. [QUOTE] Signatures of Positive Selection in Genes Associated with Human Skin Pigmentation as Revealed from Analyses of Single Nucleotide Polymorphisms http://www3.interscience.wiley.com/journal/120118254/abstract KEYWORDS human pigmentation • skin color • positive selection • genetic adaptation • Perlegen database • SNP • EHH test ABSTRACT Phenotypic variation between human populations in skin pigmentation correlates with latitude at the continental level. A large number of hypotheses involving genetic adaptation have been proposed to explain human variation in skin colour, but only limited genetic evidence for positive selection has been presented. To shed light on the evolutionary genetic history of human variation in skin colour we inspected 118 genes associated with skin pigmentation in the Perlegen dataset, studying single nucleotide polymorphisms (SNPs), and analyzed 55 genes in detail. [b]We identified eight genes that are associated with the melanin pathway (SLC45A2, OCA2, TYRP1, DCT, KITLG, EGFR, DRD2 and PPARD) and presented significant differences in genetic variation between Europeans, Africans and Asians. In six of these genes we detected, by means of the EHH test, variability patterns that are compatible with the hypothesis of local positive selection in Europeans (OCA2, TYRP1 and KITLG) and in Asians (OCA2, DCT, KITLG, EGFR and DRD2), whereas signals were scarce in Africans (DCT, EGFR and DRD2). Furthermore, a statistically significant correlation between genotypic variation in four pigmentation candidate genes and phenotypic variation of skin colour in 51 worldwide human populations was revealed. Overall, our data also suggest that light skin colour is the derived state and is of independent origin in Europeans and Asians, whereas **dark skin** color seems of unique origin, **reflecting the ancestral state in humans**.[/b] [/QUOTE] [QUOTE] The genetic architecture of normal variation in human pigmentation: an evolutionary perspective and model http://hmg.oxfordjournals.org/cgi/content/full/15/suppl_2/R176 ABSTRACT Skin pigmentation varies substantially across human populations in a manner largely coincident with ultraviolet radiation intensity. This observation suggests that natural selection in response to sunlight is a major force in accounting for pigmentation variability. We review recent progress in identifying the genes controlling this variation with a particular focus on the trait's evolutionary past and the potential role of testing for signatures of selection in aiding the discovery of functionally important genes. We have analyzed SNP data from the International HapMap project in 77 pigmentation candidate genes for such signatures. [b]On the basis of these results and other similar work, we provide a tentative three-population model (West Africa, East Asia and North Europe) of the evolutionary–genetic architecture of human pigmentation. These results suggest a complex evolutionary history, with selection acting on different gene targets at different times and places in the human past. Some candidate genes may have been selected in the ancestral human population, others in the ‘out of Africa’ proto European-Asian population, whereas most appear to have selectively evolved solely in either Europeans or East Asians separately despite the pigmentation similarities between these two populations.[/b] Selection signatures can provide important clues to aid gene discovery. However, these should be viewed as complements, rather than replacements of, functional studies including linkage and association analyses, which can directly refine our understanding of the trait. [/QUOTE]Chimu you seem to have quite a challenge ahead of you, hope you don't become frightened.... [/QB][/QUOTE]
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