The most important radiation damage has always been from the sun. Dark-skinned races are fully equipped with the primary defense against the sun’s rays, the pigment melanin in the outer skin, which protects the underlying tissues simply by shading them. A few thousand generations of free- dom from sunshine, as may happen to animal populations living in caves, results in a loss of the ability to make pigment. The continuous presence of pigmentation in dark-skinned races shows the benefits of its protection against sunshine.


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People of European descent pose a special evolutionary problem. Their pale skins show that protection from sunshine has not been such a consistently important factor in their history, and they are especially vulnerable to sunburn. The first warm, sunny days of spring tempt some of them to bare their skins for many hours. Maybe they know from painful experience that this is not wise, but it feels so good after the winter chill. If fear of repeating the previous year’.; sunburn does not deter them, the pain of this year’s will not either, because it comes too late. Only hours after exposure does the sunburned area become sore, red, and feverish. For several days, sheets of dead skin peel off. Recovery can be complete in a week or two, but this may not be the end of the story, because getting even a few serious sunburns greatly increases the risk of skin cancer years or decades later.