On the sun-drenched Caribbean island of St Thomas, there is a plant known to the locals as the tourist tree, so called because its red bark peels off in long pale strips. It should be grown more widely, as a cautionary reminder that you don't have to travel to the tropics to see fair-skinned holidaymakers burnt to a crisp. The sad fact is that some of us are woefully equipped to deal with even a little sunshine. How could evolution have played such a nasty trick? People have long assumed that pigments in our skin protect us from the sun. It seems obvious, given that the nearer the equator you go, the darker the skin of the local people. And the discovery of a link between UV and cancer has strengthened that conviction. But if dark skin is such an advantage, why are we not all as dark as possible? This has puzzled experts for decades and there has been no shortage of explanations, from the suggestion that males prefer paler women to the notion that the lack of sunshine at high latitudes has caused skin colour to fade, in much the same way that cave-dwelling animals have lost their pigmentation. But none is completely convincing.
展开▼
