EVOLUTION OF SKIN COLOR-A HISTORICAL INSIGHT

The old apartheid practices based on skin color have practically disappeared in most parts of the world while the American slavery system that used imported African people with dark colored skin remains only in memory. Probably if to day's knowledge about the role skin color plays in maintaining good health was known 300 years ago, people would have given more respect to a dark skinned person than what the latter received from their fair skinned cousins! For quiet some time knowledge about the critical role played by Vitamin D in bone formation and development was in the public domain and that this particular micro nutrient cannot be synthesized by the human body was also known. It is underneath the human skin that Vitamin D is formed from its precursors through the action of Ultra Violet Rays (UVR), so abundantly available to those living near the equator and the extent of synthesis is a function of time of exposure. The advantage of darker skin is that it not only allows synthesis of Vitamin D but also protects the skin from DNA damage eventually leading to skin cancer. It is not an accident that light skinned population generally live farther from the Equator where sun light is comparatively less and environmental temperature is low for people to be outside their homes for long time. Under such conditions protection from UV rays is not a major problem and that is how the pigmentation started declining progressively. This evolutionary development is purely a response to the environment and cannot be associated with any brain function. Thus color of the skin does not influence the IQ or any function associated with intelligence or skills. Here is a commentary on this interesting interpretation of the evolutionary development over the years.    

"The human lineage originated, and first flourished biologically and culturally, in Africa. Evolutionarily, each of us is African; the first people had darkly pigmented skin and were thus well-adapted to handle the high levels of UVR (ultraviolet radiation) in equatorial regions. As Jablonski explains in her talk, UVR has both benefits and costs for the human body. On the plus side, when it strikes the skin it catalyzes Vitamin D, which is essential for bone and immune health; on the minus side, it can cause DNA damage and skin cancers. In ancient Africa, melanin acted as a natural sun screen to protect people from the dangers while still allowing the benefits of Vitamin D synthesis from the sun. When people from some ancestral populations migrated north out of Africa, they encountered much less intense UVR. The previously adaptive sun screen of melanin was now a disadvantage, and thus lightly pigmented skin evolved. People with light skin in these northern regions spent enough time in the sun that, typically, their skin still synthesized adequate vitamin D, a process helped along in some areas by diets heavy in fish. What we have nowadays is also a balance of pluses and minuses: A lovely rainbow diversity of skin colors that reflects the map of our ancestors' relatively recent geography, and an unfortunate risk of vitamin D deficiency that comes with spending the bulk of our hours indoors in artificial light".

Vitamin D deficiency is manifested among people of all skin colors because of the new living style where exposure to sun light is progressively being reduced due to artificially lighted houses, heavy dependence on automobiles, less and less walking in the open and other undesirable practices. Of course there is a billion dollar industry riding on skin care products including sun screens which will help to some extent in lessening the dangers of incidence of cancer but choosing a right time for walking under the sun cannot  be of any risk as long as the exposure is not for long time. According to health experts even a daily 15 minutes exposure should be adequate for generating the required quantum of Vitamin D and maintain a blood level of 30 micro gram uniformly.

V.H.POTTY
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