Natural selection is furthering mutations that are making skin paler
The first hominids that appeared in Africa probably had pale skin covered with hair, like other primates. They are thought to have lost their hair when they became bipedal, and that natural selection subsequently furthered darker skins in Africa as they protect against ultraviolet (UV)light. However, when humans left Africa (about 100,000 years ago) and headed for Asia or Europe, where UV intensity was lower, they once again acquired a less pigmented skin colour. What caused the depigmentation of these populations is not clear, and two hypotheses have in fact been put forward: firstly, it could be due to a relaxing in natural selection that keeps the skin dark in Africa, since when leaving Africa, UV levels are lower; secondly, it could be due to the fact that natural selection furthers certain mutations so that individuals can have paler skin, since at these latitudes having a skin with a dark pigmentation prevents the synthesis of adequate levels of vitamin D, essential for our survival. …