Light-skinned persons have about a tenfold greater risk of dying from skin cancer under equal sunlight exposure, with redheads having the greatest risk. This can be explained by the fact that their traditional animal-based diet provides plenty of vitamin D.ĭark skin protects against ultraviolet light this light causes mutations in skin cells, which in turn cause skin cancers. The Inuit and Yupik are special cases: even though they live in an extremely sun-poor environment, they have retained their relatively dark skin. (The skin cancer connection is probably of secondary importance, since skin cancer usually kills only after the reproductive age and therefore does not exert much evolutionary pressure.) When humans migrated to less sun-intensive regions in the north, low vitamin D 3 levels became a problem and light skin color re-emerged. Once they encountered baldness, they evolved dark skin, needed to prevent low folate levels since they lived in sun-rich Africa. The evolution of the different skin tones is thought to have occurred as follows: the haired ancestors of humans, like modern great apes, had light skin under their hair. Each gene comes in several alleles, resulting in a great variety of different skin tones. One copy of each of those genes is inherited from the father while the mother contributes the other. Both amount and type are determined by four to six genes which operate under incomplete dominance. Melanin comes in two types: pheomelanin (red) and eumelanin (dark brown to nearly black).
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