We are all the same species, Earthlings.
EVOLVING SKIN
BY Beth Herbert | 16 Sep 2011
As early humans dispersed and populations moved away from the equator, lighter skin tones emerged from natural selection—why?
Melanin is a wonderful natural sunscreen, but it slows down the process of making vitamin D in the skin. Vitamin D is made from UVB radiation impinging on the skin. At high latitudes, UVB radiation is less common and more highly seasonal. If you have very darkly pigmented skin, [your] ability to make vitamin D is lessened [significantly]. I have moderately pigmented skin for a European. If I’m standing next to someone with very darkly pigmented skin and we’re both out in the middle of the summer sunshine, I will be able to make five or six times as much vitamin D in my skin in any time period as my darkly pigmented friend.
At the equator, where the sun is really intense, a darkly pigmented person will be able to make enough vitamin D through casual exposure to satisfy their physiological needs, because there’s simply so much UVB in the sunlight. But as soon as they get outside the tropics, where the UVB is less plentiful, they must spend longer and longer [periods of time in the sun] in order to get enough vitamin D to satisfy their physiological needs. Vitamin D [is] incredibly important for human health and reproductive success. Vitamin D-rich diets, including marine mammals and fish, were eaten by humans later in our evolutionary career—after we had the technology to be able to harvest foods from the sea. But early in our evolutionary career, we mostly didn’t make use of high vitamin D foods. We got our vitamin D from the sun through our skin.
As humans dispersed outside of the tropics, there was [an] intense evolutionary pressure to lose pigmentation. Modern genetics, and specifically genomic studies, have shed a lot of light on this process. People like me, who are interested in the history of evolution, or the history of adaptation—we’ve made inferences based on the fossil record [about] what we thought probably happened in human evolution. But the genomics experts have actually been able to establish unequivocally that there were independent genetic mutations that occurred in the ancestors of Western Europeans and Eastern Asians that led to loss of pigmentations as people dispersed into those areas. That’s really interesting, because both of these groups today have lightly pigmented skin, but it’s not from the same set of genetic changes. It’s from independent genetic changes that brought about loss of melanin pigment in the skin.
And, not only do we see different pathways in modern Europeans and modern Eastern Asians, but [researchers have] been able to look at the ancient DNA in Neanderthals and diagnose that they, in fact, had de-pigmented skin that was due to yet a different set of mutations. So the evolutionary pressure to lose pigment at high latitudes was great, and in at least three different instances—two groups of modern humans and one group of fossil relatives—we see three different genetic trajectories for achieving loss of pigmentation.
Nina Jablonski (photo courtesy of Pennsylvania State University)
http://youtu.be/QOSPNVunyFQ
everyone is so damn sensitive these days.. Waa waa waa 
