The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [7]
It is one of the remarkable things about the human race that no two people are identical. No father is exactly recast in his son; no daughter is exactly like her mother; no man is his brother’s double and no woman a carbon copy of her sister – unless they are that rarity, a pair of identical twins. Every idiot can be father or mother to a genius – and vice versa. Every face and every set of finger prints is effectively unique. Indeed, this uniqueness goes further in human beings than in any other animal. Whereas every deer, or every sparrow, is self-reliant and does everything every other deer or sparrow does, the same is never true of a man or a woman and has not been for thousands of years. Every individual is a specialist of some sort, whether he or she is a welder, a housewife, a playwright or a prostitute. In behaviour, as in appearance, every human individual is unique.
How can this be? How can there be a universal, species-specific human nature when every human being is unique? The solution to this paradox lies in the process known as sex. For it is sex that mixes together the genes of two people and discards half of the mixture, so ensuring that no child is exactly like either of its parents. And it is also sex that causes all genes to be contributed eventually to the pool of the whole species by such mixing. Sex causes the differences between individuals but ensures that those differences never diverge far from a golden mean for the whole species.
A simple calculation will clarify the point. Every human being has two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents, and so on. A mere thirty generations back – in, roughly, 1066 AD – you had more than a billion direct ancestors in the same generation (2 to the power of 30). Since there were fewer than a billion people alive at that time in the whole world, many of those people were your ancestors twice or three times over. If, like me, you are of British descent, the chances are that almost all of the few million Britons alive in 1066, including King Harold, William the Conqueror, a random serving wench and the meanest vassal (but excluding all well-behaved monks and nuns) are your direct ancestors. This makes you a distant cousin many times over of every other Briton alive today except the children of recent immigrants. All Britons are descended from the same set of people, a mere thirty generations ago. No wonder there is a certain uniformity about the human (and every other sexual) species. Sex imposes it by its perpetual insistence on the sharing of genes.
If you go back further still, the different human races soon merge. Little more than three thousand generations back, all of our ancestors lived in Africa, a few million simple hunter-gatherers, completely modern in physiology and psychology.6 As a result, the genetic differences between the average members of different races are actually tiny and are mostly confined to a few genes that affect skin colour, physiognomy or physique. Yet the differences between any two individuals, of the same race or of different races, can still be large. According to one estimate, only seven per cent of the genetic differences between two individuals can be attributed to the fact that they are of different race; eighty-five per cent of the genetic