The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [20]
Williams was inclined to conclude that perhaps his logic was good, but for animals like us the practical problems were simply insurmountable. In other words, getting from being sexual to being asexual would indeed confer advantages, but it would be just too difficult to achieve. About this time, sociobiologists were beginning to fall into a trap of being too readily enamoured of ‘adaptationist’ arguments: just-so stories, as Stephen Jay Gould of Harvard called them. Sometimes, he pointed out, things were the way they were for accidental reasons. Gould’s own example is of the triangular space between two cathedral arches at right angles, known as a spandrel, which has no function but is simply the by-product of putting a dome on four arches. The spandrels between the arches of St Mark’s Basilica in Venice were not there because somebody wanted spandrels. They were there because there is no way to put two arches next to each other without producing a space in between. The human chin may be such a spandrel – it has no function but is the inevitable result of having jaws. Likewise the fact that blood is red is surely a photochemical accident, not a design feature. Perhaps sex was a spandrel, an evolutionary relic of a time when it served a purpose. Like chins, little toes or appendixes, it no longer served a purpose, but was not easily got rid of.22
Yet this argument for sex is pretty unconvincing, because quite a few animals and plants have abandoned sex or have it only occasionally. Take the average lawn. The grass in it never has sex – unless you forget to cut it, at which point it grows flower-heads. And what about water fleas? For many generations in a row, water fleas are asexual: they are all female, they give birth to other females, they never mate. Then as the pond fills up with water fleas some start to give birth to males, which mate with other females to produce ‘winter eggs’ that lie on the bottom of the pond and regenerate when the pond is flooded again. Water fleas can turn sex on and off again, which seems to prove that it has some immediate purpose beyond helping evolution to happen. It is worth an individual water flea’s while to have sex, at least in certain seasons, if it intends to leave descendants.
So we are left with an enigma. Sex serves the species, but at the expense of the individual. Individuals could abandon sex and rapidly outnumber their sexual rivals. But they do not. Sex must therefore in some mysterious manner ‘pay its way’ for the individual as well as for the species. How?
Provocation by Ignorance
Until the mid 1970s, the debate that Williams had started remained an arcane and obscure one. And the protagonists had sounded fairly confident in their attempts to resolve the dilemma. But in the mid 1970s, two crucial books changed that forever by throwing down a gauntlet that other biologists could not resist picking up. One book was by Williams himself, the other by Maynard Smith.23 ‘There is a kind of crisis at hand in evolutionary biology,’ wrote Williams melodramatically. But whereas Williams’s book Sex and Evolution was an ingenious account of several possible theories of sex – an attempt to defuse the crisis – Maynard Smith’s book The Evolution of Sex was very different. It was a counsel of despair and bafflement. Again and again, Maynard Smith came back to the enormous price of sex: the twofold disadvantage – two parthenogenetic virgins can have twice as many babies as one woman and one man. Again and again, he declared it insurmountable by current theories. ‘I fear the reader may find these models insubstantial and unsatisfactory,’ he wrote. ‘But they are the best we have.’ And in a separate paper: ‘One is left with the feeling that some essential