Why do humans not have blue or green hair? Insects have these hues, birds are so plumaged, and even the mandrill baboon has blue pigmentation on the face. We humans have blue or green eyes, so the ability to produce the colors in question is present. So why, oh why, must we resort to artificial means to achieve blue or green hair? And I don’t mean the sort of “blue rinse” fashionable for ladies of a certain age. I mean royal blue, sky blue, even Wedgwood blue. As for green, I rather fancy a shimmering kelly green. –Al in Beantown
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Al, if you were in high school now you would be on the cutting edge. There are two lines of thought on why green, blue, etc, don’t naturally occur. The first is that all kids born with such hair due to random mutation were spontaneously murdered by their parents, obviously a highly retro point of view. The second is that green and blue confer no reproductive advantage, a contention that, at the risk of sounding a little retro myself, is not going to get any argument from me.
(2) Hair-color variation may be more complicated than you think. Mark Lomas of Cambridge, England (Cecil has been fooling around on the Internet again), offers the following illustrative tidbit: a disproportionate number of the cats found run over by cars on British roads are white. Why? Turns out white cats are usually deaf and are saved from otherwise certain extinction only by the humans who breed them. Lomas’s point is that the genetic change necessary to obtain blue or green hair in humans might have disastrous side effects that would prevent the trait from being passed on.
