If apparently humans originally migrated out of Africa...how did our skins change to become so diverse?

Question

Could colder weather have anything to do with the development of lighter coloured skin?

Answer 1

Low ultraviolet levels are the clincher.

Africans get mutations for skin colour as often as the Northern latitude people, it's just that the very high UV levels select out even minor lightening mutations pretty swiftly.

European and East Asian light skin tones come from two different mutations, so our populations had split up already when those changes occurred. So European/Asian ancestors probably split from each other in a very sunny land. It's why Europeans are 'pink' and Asians 'golden'.



Mutations for light skin get selected into a population if the ultraviolet levels are low, as exposure sunlight is the main way humans acquire vitamin D. In cold climates most of the skin will be covered most of the year round, so there will be even more incentive for the skin to lighten up.

The only exception to the 'light skin/low UV' rule are the Eskimos. They eat so much vitamin D rich fish that skin lightening hasn't been necessary.

Answer 2

Over time, the darker skin melanins were not selected as much by successive generations, as vitamin D needed to be more efficiently absorbed from sunlight, which became challenging, the further humans traveled from the Equator!

Also, folic acid didn't need as much dark melanin in the skin, to protect women during childbirth, as they did, closer to the Equator!

Answer 3

it was the exposure to the sun due to long treks trying to find new resources and settlements or something along those lines.

Answer 4

• We humans did start out in Africa, and we were all black.

The out of Africa migration was done during the first half of the Pleistrocence period. It was a time of ice ages, when sea levels dropped significantly and there was increased rainfall in many regions. At the same time Homo erectus was making stone tools and was able to use fire. The question of his being able to create fire has not yet been answered. Given the favorable climate and the increased skills to control his environment, Homo erectus spread out of Africa.

As for skin color:

"In their analysis of human evolutionary history, Jablonski and Chaplin concluded that modern humans most likely evolved in the tropics, where they were exposed to high UV levels. But as they moved into regions away from the equator, where UV levels are lower, humans became fairer so as to allow enough UV radiation to penetrate their skin and produce vitamin D, the "sunshine vitamin," also obtained from eating fish and marine mammals. Vitamin D is essential for maintaining healthy blood levels of calcium and phosphorous, and thus promoting bone growth.

Skin color, according to Jablonski and Chaplin, basically becomes a balancing act between the evolutionary demands of photo-protection and the need to create vitamin D in the skin.

One of the important implications of Jablonski and Chaplin's work is that it underlines the concept of race as purely a social construct, with no scientific grounds. DNA research has shown that genetically all humans, regardless of skin color and other surface distinctions, are basically the same. In an April 2001 article titled, "The Genetic Archaeology of Race," published in the Atlantic Monthly, Steve Olson writes "the genetic variants affecting skin color and facial features are essentially meaningless —they probably involve a few hundred of the billions of nucleotides in a person's DNA. Yet societies have built elaborate systems of privilege and control on these insignificant genetic differences."

http://ngm.nationalgeographic.com/ngm/02...

"Before the mass global migrations of people during the last 500 years, dark skin color was mostly concentrated in the southern hemisphere near the equator and light color progressively increased further away, as illustrated in the map below. In fact, the majority of dark pigmented people lived within 20° of the equator. Most of the lighter pigmented people lived in the northern hemisphere north of 20° latitude."

http://anthro.palomar.edu/adapt/adapt_4....

Answer 5

White people are from Africa.  They travelled from Africa to Europe, which is at a different position to the sun.  This could have affected skin color.  Also, the hotter climate could make humans evolve darker skin to overcome diseases such as cancer.  Likewise, when an adaptation is no longer needed, it disappears (changing from black to white skin).

Anyway, this is what I heard once!