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Why no blue hair? (request for comments)
Edward Zotti (ezotti@merle.acns.nwu.edu)
17 Dec 94 23:40:59 GMT
My employer, the legendary Cecil Adams, has asked me to post the following
draft column, written in response to a letter from a reader of his legendary
newspaper column, the Straight Dope. The column is based in part on responses
generously contributed by participants in this group. Further comments,
corrections, etc., are invited. Replies by e-mail appreciated.
Copyright 1994 Chicago Reader
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
Wedgewood blue. As for green, I rather fancy a shimmering kelly
green. --Al in Beantown
Al, if you were in high school now, you would be on the
cutting edge. There are two schools 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.
Beyond that it is difficult to say anything definite. As one
member of the Straight Dope Science Advisory Board plaintively
notes, "why don't humans have beaks?" However, the SDSAB has come
up with the following thoughts:
(1) In animals bright colors are a means of sexual display.
For this purpose we humans have thong bikinis and bicep tattoos,
or, more seriously, enlarged mammary glands and (potentially) long
head hair of whatever color. Hair color, it is widely thought,
originally served the purely practical purpose of shielding us from
the sun, which is why peoples indigenous to northern climates tend
to be blond (less of the protective pigment melanin) while those
living farther south tend to be brunettes. That does leave us with
the difficulty of explaining red hair, but we will leave that to
another day and with luck another columnist.
(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.
But there may be more to it than that. Lomas notes that green
and blue hair in humans is not merely rare; it is unheard of. That
suggests that adding another shade to the usual human hair color
palette might require simultaneous changes to multiple genes, a
highly unlikely event. Darn.
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