The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [43]
As it happens, the rotifer scandal may be on the verge of a solution. But, in the best traditions of the science of sex, it could still go either way. Two new theories to explain the sexlessness of bdelloid rotifers each point to different explanations.
The first is Matthew Meselson’s. He thinks that genetic insertions – jumping genes that insert copies of themselves into parts of the genome where they do not belong – are for some reason not a problem for rotifers. So they do not need sex to purge them from their genes. It’s a Kondrashov-like explanation, though with a touch of Hamilton (Meselson calls insertions a form of venereal genetic infection).68 The second is a more conventional Hamiltonian idea. Richard Ladle of Oxford University noticed that there are groups of animals that are capable of drying out altogether without dying – losing about ninety per cent of their water content. This requires remarkable biochemical skill. And none of them have sex. They are tardigrades, nematodes and bdelloid rotifers. Some rotifers, remember, dry themselves out into little tuns and blow around the world in dust. This is something sexual monogonont rotifers cannot do (although their eggs can). Ladle thinks that drying yourself out may be an effective anti-parasite strategy – a way of purging the parasites from your body. He cannot yet explain exactly why the parasites mind being dried out more than their hosts do; viruses are little more than molecular particles in any case and so could surely survive a good drying. But he seems to be on to something. Those nematode or tardigrade species that do not dry out are sexual. Those that can dry out are all-female.69
The Red Queen has by no means conquered all her rivals. Pockets of resistance remain. Genetic-repair die-hards hold out in places like Arizona, Wisconsin and Texas. Kondrashov’s banner still attracts fresh followers. A few lonely tangled bankers snipe from their laboratories. John Maynard Smith pointedly calls himself a pluralist still. Graham Bell says he has abandoned the ‘monolithic confidence’ (in the tangled bank) that infused his book The Masterpiece of Nature, but has not become an undoubting Red Queener. George Williams still hankers after his notion that sex is a historical accident that we are stuck with. Joe Felsenstein maintains that the whole argument was misconceived, like a discussion of why goldfish do not add to the weight of the water when added to a bowl. Austin Burt takes the surprising view that the Red Queen and the Kondrashov mutation theory are merely detailed vindications of Weismann’s original idea that sex supports the variation needed to speed up evolution: that we have come full circle. Even Bill Hamilton concedes that the pure Red Queen probably needs some variation in space as well as time to make her work. Hamilton and Kondrashov met for the first time in Ohio in July 1992 and agreed convivially to differ until more evidence was in. But scientists always say that: advocates never concede defeat. I believe that a century hence biologists will look back and declare that the Vicar of Bray fell down a tangled bank and was slain by the Red Queen.70
Sex is about disease. It is used to combat the threat from parasites. Organisms need sex to keep their genes one step ahead of their parasites. Men are not redundant after all; they are woman’s insurance policy against her children being wiped out by influenza and smallpox (if that is a consolation). Women add sperm to their
eggs because if they did not, the resulting babies would be identically vulnerable to the first parasite that picked their genetic locks.
Yet before men begin to celebrate their new role, before the fireside drum-beating sessions incorporate songs about pathogens, let them tremble before a new threat to the purpose of their