# Question re: evolution and coming out of Africa **URL:** \ **Category:** Factual Questions\ **Created:** [August 9, 2005, 4:41pm UTC](https://boards.straightdope.com/t/question-re-evolution-and-coming-out-of-africa/316290 "2005-08-09T16:41:12Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Electronic\_Chaos](https://avatars.discourse-cdn.com/v4/letter/e/bbe5ce/32.png) [@Electronic\_Chaos](https://boards.straightdope.com/u/Electronic_Chaos)\ **Post date:** [August 9, 2005, 4:41pm UTC](https://boards.straightdope.com/t/question-re-evolution-and-coming-out-of-africa/316290/1 "2005-08-09T16:41:12Z")
(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? ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [August 9, 2005, 5:13pm UTC](https://boards.straightdope.com/t/question-re-evolution-and-coming-out-of-africa/316290/2 "2005-08-09T17:13:21Z")
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. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 9, 2005, 5:30pm UTC](https://boards.straightdope.com/t/question-re-evolution-and-coming-out-of-africa/316290/3 "2005-08-09T17:30:03Z")
Selection for skin color has probably been mainly on the basis of vitamin D production and vitamin B retention. From [here](http://en.wikipedia.org/wiki/Human_skin_color) > [@](#): > > Dark skin protects against skin cancer, mutations in skin cells induced by ultraviolet light. Light-skinned persons have about a tenfold greater risk of dying from skin cancer under equal sun conditions. Furthermore, dark skin prevents UV-A radiation from destroying the essential B vitamin folate. Folate is needed for the synthesis of DNA in dividing cells and too low levels of folate in pregnant women are associated with birth defects. > > While dark skin protects vitamin B, it can lead to a vitamin D deficiency. The advantage of light skin is that it lets more sunlight through, which leads to increased production of vitamin D3, necessary for calcium absorption and bone growth. The lighter skin of women results from the higher calcium needs of women during pregnancy and lactation. > > The evolution of the different skin colours is thought to have occurred as follows: the haired ancestor of humans, like modern great apes, had light skin under their hair. Once the hair was lost, they evolved dark skin, needed to prevent low folate levels since they lived in sun-rich Africa. (The skin cancer connection is probably of secondary importance, since skin cancer usually kills only after the reproductive age and therefore doesn’t exert much evolutionary pressure.) When humans migrated to sun-poorer regions in the north, low vitamin D3 levels became a problem and light skin colour evolved. > > Dark-skinned people who live in sun-poor regions often lack vitamin D3, one reason for the fortification of milk with vitamin D in some countries. 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. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [August 9, 2005, 6:52pm UTC](https://boards.straightdope.com/t/question-re-evolution-and-coming-out-of-africa/316290/4 "2005-08-09T18:52:09Z")
> [@Electronic Chaos](#): > > So what caused the darker skinned gene-carriers to die out and the lighter skinned ones to live on in Europe? 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](http://en.wikipedia.org/wiki/Allele) (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).