Question re: evolution and coming out of Africa

(This may be GD material, and if so please kindly move it, Mods)

As I understand it, Homo Sapiens originated in Africa. We lingered there awhile, and then some of us wandered off to populate Europe, Asia, and even eventually cross the great landbridge and populate America. Also, from my understanding being in Africa and close to the equator, we developed dark skin pigmentation to protect us from the sun. But somehow after leaving Africa we lost the dark skin pigmentation. For that to happen, there had to have been some sort of advantage to having light skin, correct? So what caused the darker skinned gene-carriers to die out and the lighter skinned ones to live on in Europe?

I’m not a biologist (surely one will quickly come around), but I recall hearing that it has something to do with vitamin D production. the human body can produce vitamin D autonomously; the process involves sunlight exposure of the skin. In regions with reduced sunlight intensity, brighter skin might be advantageous in this respect compared to darker skin pigmentation.

Selection for skin color has probably been mainly on the basis of vitamin D production and vitamin B retention.

From here

There have been at least 5 threads on this subject in the last 18 months; a search on “vitamin skin color Africa” will bring them up.

Your question presuposes an factual error or two. Firstly, there is more than one gene that codes for skin color, so it’s not so much that certain people “died out” but that ratio of the various alleles (2 alleles = 1 gene for humans) changed over time. Seconldy, people didn’t have to “die out” for this to happen, it’s just that people with ligher skin (ie, a different arrangement of alleles) were more successful in producing offspring (ie, passing those alleles on too the next generation).