no! the lack of sunlight did.....
there are nig nogs with white in their blood..the bio quality of whiteness. it is them who became white in the cold.
Vitamin D is the issue here and its essential nature in the human body. it does not occur in the human body but it is essential for bone structure and reproduction. if you cant get it from the sunlight and your food you are going to die..you will lose containment and cant push to to get babies out for pregnant women.
but if there is limited sunlight and your skin is white you can make do. black skin..melanin.. will get you dead in a situation of limited sunlight. black skin is an advantage in powerful sunlight. it is a serious and fatal disadvantage in the cold.
well the glacier retreated around 50-40 thousand years ago and nig nogs penetrated into europe where they met neantherthall. then the ice came back trapping populations up there. and those are the conditions that led to whiteness..black people shedding their blackness..those with a biological propensity to whiteness.
the triggering factor is an enzyme called tyrosinase. check it out! educate yuhself. see what tyr can do in your body
there were black people from ancient times in Russia up to Stalin times..in China up to Mao's time. Mao is reputed to have been very hard on them. in Russia around lake Lake Baikal region is where they proliferated and remained black.
reason! plentiful supply of cod...rich in Vitamin D.. the major food they ate. they did not need sun to survive and stay black