Young Black Girl On The White Bed

Physiological traits
• Dark skin
The evolution of dark skin is linked intrinsically to the loss of body hair in humans. By 1.2 million years ago, all people having descendants today had the same receptor protein of today's Africans; their skin was dark, and the intense sun killed off the progeny with any lighter skin that resulted from mutational variation in the receptor protein. This is significantly earlier than the speciation of Homo sapiens from Homo erectus some 250,000 years ago.
Skin cancer as a result of ultraviolet light radiation causing mutations in the skin is less common among people with dark skin than it is among those with light skin. Furthermore, dark skin prevents an essential B vitamin, folate, from being destroyed. Therefore, in the absence of modern medicine and diet, a person with dark skin in the tropics would live longer, be healthier and more likely to reproduce than a person with light skin. White Australians have some of the highest rates of skin cancer as evidence of this expectation. Conversely, as dark skin prevents sunlight from penetrating the skin it hinders the production of vitamin D3. Hence when humans migrated to less sun-intensive regions in the north, low vitamin D3 levels became a problem and lighter skin colors started appearing. White people of Europe, who have low levels of melanin, naturally have an almost colorless skin pigmentation, especially when untanned. This low level of pigmentation allows the blood vessels to become visible which gives the characteristic pale pink color of white people. The loss of melanin in white people is now thought to have been caused by a mutation in just one letter out of 3.1 billion letters of DNA.