Light skin was favored by natural selection in northern climes. Sun strikes skin, forms Vitamin D, which is absorbed and causes better pelvic development for child bearing. It is quite likely that Neanderthals were predominantly fair skinned, blue eyed, redheads. Homo sapiens out of Africa did not do well in the far north until the white gene mutation occurred, perhaps 30 or 40,000 years ago, allowing for more successful childbirth.
Homo sapiens out of Africa did not do well in the far north until the white gene mutation occurred...s/b "got it from the union with the Neandertal." :')
A big hole in this theory: blacks in North America have no problem producing babies no matter where they live, and they aren't eating many fish livers. The evolutionary pressure of vitamin D deficiency is insufficient to explain how suddenly white skin, not just light skin, appeared. My hypothesis is that white skin, blond hair, blue eyes are mostly cosmetic traits, and they are not mostly from sexual selection but from mothers cultivating them in their children. The temporary blond/blue in most European babies is strong evidence for this. The blond hair doesn't disappear until about age 5, when a child is no longer so dependent on mom. Do you have an alternate explanation for this phenomenon? What purpose does it serve other than cosmetic?