Where does white skin come from?

时间:2019-03-01 05:14:01166网络整理admin

By Anil Ananthaswamy THE idea that early humans became fair-skinned as they migrated north out of Africa so they could make enough vitamin D to stay healthy has been questioned again, reopening a debate that many think is settled. In equatorial Africa and in the tropics, melanin – the pigment that makes skin dark – provides protection against the intense sunlight. But melanin can also block the ultraviolet radiation (UVB) that triggers vitamin D production in the skin. This is an advantage in the tropics,