# Evolution, Skin Pigment and Migration/ Weather **URL:** \ **Category:** Factual Questions\ **Created:** [March 5, 2004, 7:36pm UTC](https://boards.straightdope.com/t/evolution-skin-pigment-and-migration-weather/232750 "2004-03-05T19:36:51Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [March 5, 2004, 7:36pm UTC](https://boards.straightdope.com/t/evolution-skin-pigment-and-migration-weather/232750/1 "2004-03-05T19:36:51Z")
A few disclaimers, please. This is NOT a Great Debate. This is NOT a Pit Rant on skin color or race, or anything of that ilk. I have a very specific question for Anthropologists and students of Evolution and Science. It’s a volatile O.P., and I hereby request that anyone who feels the need to stray in any way from my O.P. and intent, open a separate thread in the proper forum. Please don’t turn this into something it is not. I absolutely ascribe to the theory of Evolution, that we evolved from Great Apes. Now then. There I stood, on the commuter train last night, my back against the door, facing a carful of people. Almost all white people. Something clicked in my head, and I thought about Polar Bears. They have black skin, and clear hair follicles, so that the U.V. coming in towards them, so that the U.V. can more efficiently warm their skin- in the cold northern climes. This gets me wondering. Why is it that primates and the Great Apes we descended from, have darker skin when it is irrefutably accepted by anthropologists that Early Man/Woman came out of sub-Saharan Africa ? Why is it that lighter skinned primates did not develop, there in the blisteringly hot U.V.-filled African veldt?? Why is it that as the pre-human and proto-humans spread out across Pangea, that their skin color didn’t darken- just as a polar bear’s did, to make maximum use of the meagre U.V. coming into far northern and far southern climes? Why did it happen in exactly opposite patterns from that which kind of makes sense to me? Why aren’t primates pale pale pink skinned? Cartooniverse ---
**Author:** ![dinoboy](https://avatars.discourse-cdn.com/v4/letter/d/65b543/32.png) [@dinoboy](https://boards.straightdope.com/u/dinoboy)\ **Post date:** [March 5, 2004, 7:51pm UTC](https://boards.straightdope.com/t/evolution-skin-pigment-and-migration-weather/232750/2 "2004-03-05T19:51:57Z")
But the [ancestral](http://www.biosci.ohio-state.edu/~eeob/eeob400/Handout3.pdf) condition of skin in primates is believed to be pale… [Here](http://www.pbs.org/wgbh/evolution/library/07/3/l_073_04.html) is another site. ---
**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:** [March 5, 2004, 8:00pm UTC](https://boards.straightdope.com/t/evolution-skin-pigment-and-migration-weather/232750/3 "2004-03-05T20:00:42Z")
One of the critical issues for humans is the need for sunlight in order to manufacture Vitamin D. 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. > > 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 either from sexual preference or from the higher calcium needs of women during pregnancy and lactation. > > The evolution of the different skin colors 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 color 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. ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [March 5, 2004, 11:39pm UTC](https://boards.straightdope.com/t/evolution-skin-pigment-and-migration-weather/232750/4 "2004-03-05T23:39:18Z")
Well. Thank you. That was quick. I understand your answer, and it makes a lot of sense. 🙂