Armand Leroi, "a Reader in Evolutionary Developmental Biology at Imperial College, London. He is the author of Mutants: On Genetic Variety and the Human Body, winner of The Guardian First Book Award, 2004.
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Cyclopia is caused by a deficiency in a gene called Sonic hedgehog. Sonic hedgehog is named after a fruit fly gene which when mutated causes bristles to sprout all over the fruit fly larva, hence 'hedgehog'. When the gene was found in mammals, some wit called it Sonic hedgehog after the video game character. If you get rid of this gene, bad things happen. You lose your arms beneath the elbow and legs beneath the knee. The face collapses in on itself, such that you get a single eye in the middle of the forehead and the rest of the face collapses into a long, trunk-like proboscis. The forebrain, which is normally divided such that we have a left and a right brain—the left and right cerebral hemispheres—is fused into a single unitary structure. Indeed the technical name for this syndrome is called Holoprosencephaly. …
[T]hese days anthropologists and geneticists overwhelmingly emphasise the similarities among people from different parts of the world at the expense of the differences. From a political point of view I have no doubt that's a fine thing. But I suggest that it's time that we grew up. I would like to suggest that actually by emphasizing the similarities but ignoring the differences, we are turning away from one of the most beautiful problems that modern biology has left: namely, what is the genetic basis of the normal variety of differences between us? What gives a Han Chinese child the curve of her eye? The curve I read once described by an eminent Sinologist as the purest of all curves. What is the source of that curve? And what gives a Solomon Islander his black-verging-on-purple skin? Or what makes red hair?
Actually, the last is the one thing we do know. It turns out that red hair is due to a mutation in a gene called MC1R, melanocortin receptor 1, which controls the production of p eumelanin, black pigment, versus red pigment, phaeomelanin. Rather marvellously, it also turns out that mutations in MCIR also cause red hair in red setters, Scottish cattle, and red foxes. But we don't know what causes brown eyes versus blue eyes versus green eyes. We know very little about the variation in normal human height. We don't know why some girls have big breasts and some of them have small breasts. These are important questions — or at least jolly interesting ones—and we just don't know their answers.
The reason I love the problem of normal human variety is because, almost uniquely among modern scientific problems, it is a problem that we can apprehend as we walk down the street. We live in an age now where the deepest scientific problems are buried away from our immediate perception. They concern the origin of the universe. They concern the relationships of subatomic particles. They concern the nature and structure of the human genome. Nobody can see these things without large bits of expensive equipment. But when I consider the problem of human variety I feel as Aristotle must have felt when he first walked down to the shore at Lesvos for the first time. The world is new again. What is more, it is a problem that we can now solve, a question we can now answer. And I think we should.
Of course, there will be people who object. There will be people who will say that this is a revival of racial science. Perhaps so. I would argue, however, that even if this is a revival of racial science, we should engage in it for it does not follow that it is a revival of racist science. Indeed, I would argue, that it is just the opposite. How shall I put it? If you want to prove, what most of us believe, that skin colour does not give the measure of a man, that it tells nothing about his abilities or temperament—then surely the best way is to learn about the genetics of skin colour and the genetics of cognitive ability and demonstrate that they have nothing to do with each other?
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