Why Oh Why Can't We Have a Better Press Corps? (Washington Post Edition)
Matthew Yglesias on the Bed-Wetters

Melanin Level Blogging

From National Geogrqphic:

Skin Online Extra: Melanin, the brown pigment in the skin, acts as a natural sunscreen. It protects against UV, and populations in the tropics are darker skinned since there is more sunlight where they live. UV ages the skin, causes skin cancer, and--most significant to Jablonski and Chaplin's work—-breaks down folate, essential vitamin B needed for cell division and producing new DNA. Pregnant women in particular require large amounts of folate to support rapid cell division in the embryo.... So if a higher melanin level is so beneficial, why isn't everyone dark-skinned?

Jablonski and Chaplin concluded that modern humans... evolved in the tropics, where they were exposed to high UV levels. But... 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... essential for maintaining healthy blood levels of calcium and phosphorous, and thus promoting bone growth. Skin color... becomes a balancing act between the evolutionary demands of photo-protection and the need to create vitamin D in the skin.

But things aren't always what they ought to be. That is the case with Eskimos and other inhabitants of northern Alaska and northern Canada. "Looking at Alaska, one would think that the native people should be pale as ghosts," Jablonski says. One of the reasons they're not is that these populations have not lived in the region very long in terms of geological time. But more importantly, their traditional diet is rich in fish and other seafood.... "What's really interesting is that if these people don't eat their aboriginal diets of fish and marine mammals, they suffer tremendously high rates of vitamin D-deficiency diseases such as rickets in children and osteoporosis in adults," Jablonski says...

Interesting that the Eskimos have not lived long enough near the North Pole for their skin color to evolve...

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