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who first pointed out that a huge false assumption lay and, indeed, still lies at the core of most popular treatments of evolution. The old concept of the ladder of progress still lingers on in the form of a teleology: evolution is good for species and so they strive to make it go faster. Yet it is stasis, not change, that is the hallmark of evolution. Sex, and gene repair and the sophisticated screening mechanisms of higher animals to ensure that only defect-free eggs and sperm contribute to the next generation – all these are ways of preventing change. The coelacanth, not the human, is the triumph of genetic systems because it has remained faithfully true to type for many millions of generations despite endless assaults on the chemicals that carry its heredity. The old Vicar of Bray model of sex, in which sex is an aid to faster evolution, implies that organisms would prefer to keep their mutation rate fairly high – since mutation is the source of all variety – and then do a good job of sieving out the bad ones. But, as Williams put it, there is no evidence yet found that any creature ever does anything other than try to keep its mutation rate as low as possible. It strives for a mutation rate of zero. Evolution depends on the fact that it fails.19

Tangled banks work, mathematically, only if there is a sufficient advantage in being odd. The gamble is that what paid off in one generation will not pay off in the next, and that the longer the generation, the more this is so – which implies that conditions keep changing.

The Red Queen

Enter, running, the Red Queen. This peculiar monarch became part of biological theory twenty years ago and has been growing ever more important in the years since then. Follow me, if you will, into a dark labyrinth of stacked shelves in an office at the University of Chicago, past ziggurats of balanced books and three-foot Babels of paper. Squeeze between two filing cabinets and emerge into a Stygian space the size of a broom cupboard, where there sits an oldish man in a checked shirt, with a grey beard that is longer than God’s but not as long as Charles Darwin’s. This is the Red Queen’s first prophet, Leigh Van Valen, a single-minded student of evolution. One day in 1973, before his beard was so grey, Van Valen was searching his capacious mind for a phrase to express a new discovery he had made while studying marine fossils. The discovery was that the probability that a family of animals will become extinct does not depend on how long that family has already existed. In other words, species do not get better at surviving (nor do they grow feeble with age, as individuals do). Their chances of extinction are random.

The significance of this discovery had not escaped Van Valen, for it represented a vital truth about evolution that Darwin had not wholly appreciated. The struggle for existence never gets easier. However well a species may adapt to its environment, it can never relax, because its competitors and its enemies are also adapting to their niches. Survival is a zero-sum game. Success only makes one species a more tempting target for another rival species. Van Valen’s mind went back to his childhood and lit upon the living chess pieces that Alice encountered beyond the looking glass. The Red Queen is a formidable woman who runs like the wind but never seems to get anywhere:

‘Well, in our country,’ said Alice, still panting a little, ‘you’d generally get to somewhere else – if you ran very fast for a long time, as we’ve been doing.’

‘A slow sort of country!’ said the Queen. ‘Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!’20

‘A new evolutionary law’, wrote Van Valen and sent a manuscript to each of the most prestigious scientific journals in turn – only to see it rejected. Yet his claim was justified. The Red Queen has become a great personage in the biological court. And nowhere has she won a greater reputation than in theories of sex.21

Red Queen theories hold