Monday, February 12, 2007

Naked in the sun

Like many snow birds to the island, I love being almost naked in the sun. I love the play on skin of sunlight, salt and sea breezes, the occasional warm rain, the whole sensational tropical feast of it. I love the feel of snow on skin too, but with snow you never have quite so much skin exposed.

I know too that evolution didn't prepare me for the tropics. My skin is dark enough that I don't burn, but the specter of melanoma is always lurking about like a dark shadow.

Here's the trick:

Ultraviolet light damages DNA and also destroys the folic acid necessary for DNA synthesis. Bad. Ultraviolet light is necessary to make vitamin D, without which we cannot incorporate calcium into our bones. Good. So we are caught between a rock and a hard place, between melanoma and rickets.

Evolution, in it's leisurely wisdom, carefully forged the necessary balance between too much ultraviolet and not enough by adjusting pigmentation in the skin. My Bahamian neighbors, whose ancestors came from equatorial Africa, are well suited for the climate here. My ancestors were mostly northern European; I have no business running around half-naked in the sun.

Still, what can you do? Culture has outraced natural selection. Descendants of tropical peoples now live in great numbers in northern cities, and northerners like me have migrated to sunnier climes. For the latter, sun cream and shade are in order -- which I blithely and dangerously ignore as I sprawl in my beach chair reading a review of Nina Jablonski's Skin: A Natural History.