Have you ever seen Spode eat asparagus?” asks a character in P.G. Wodehouse's The Code of the Woosters. “Revolting. It alters one's whole concept of Man as Nature's last word.”

Revolting it may be, but now we know that Spode, and indeed the rest of us, are about as good as Nature intends us to be. Warming to a theme that he has been exploring for many years, Professor Steve Jones tells us that evolution is over, that Man has reached a biological pinnacle, from which we can expect little improvement, that natural selection has more or less come to a standstill in the West.

There was always a strong streak of pessimism in the professor's view of the world, but at least he gives it to us straight: “If you're worried about what Utopia is going to be like, you shouldn't do,” he says. “You're living in it now.” His case, first outined at the Royal Society of Edinburgh in 2002, was presented in its starkest form in a lecture at University College London yesterday, and it remains as controversial as it was then - which is just what Professor Jones intends it to be. With the economic world clattering around our ears and climate change threatening our future, this is a fine time to learn that we inhabit Utopia.

But his arguments, as ever, are worth listening to. Essentially, he claims that the three principal drivers of human evolution - natural selection, mutation and random change - have been neutralised, at least in the West; that natural selection scarcely applies any more because our standards of health have improved so far that we no longer have to strive to survive; that mutation has reduced because older men, whose sperm produces the highest rate of cell variation, are not having as many children as they once did; and that random change is diminishing because the growth in the world population means that we are intermarrying more and becoming steadily less distinguishable.

“History is made in bed,” Professor Jones says, “but nowadays the beds are getting closer together. We are mixing into a global mass, and the future is brown.”

It's all too easy to pick holes in the argument, but most of them have been picked by Professor Jones already. He admits that a natural calamity - a new Ice Age, or a mass epidemic - might prove him wrong in the next 10,000 years, but points out, quite reasonably, that he won't be around to defend his position. He concedes that, in places such as Africa, where an entire population is fighting the HIV epidemic, the process of developing natural resistance to the disease is still taking place, making the continent a case study in evolution. And he seems to make an important concession to his critics when he points out that if evolution were ever to come to a complete halt then we would be doomed. It is, he says, like a bicycle. You can slow down and still stay on, but if it stops, you fall off.

The biggest objection to the Jones view is that predictions made from one particular moment can be swamped a few thousand years later, by forces of which as yet we know nothing. Anyone looking at Stone Age people who lived 50,000 years ago would have assumed that they would gradually become bigger and stronger. Instead, they were replaced over a relatively short evolutionary period by lighter, taller, intelligent races who migrated from Africa and populated the rest of the world. As Professor Chris Stringer, of the Natural History Museum, pointed out when the Jones theory first emerged: “You simply cannot predict evolutionary events like this.”

But what you can predict is an evolution of the mind. It may well be that physically we have reached a state that will be around for a long time to come, but what seems incontrovertible is that the way we think is changing almost in the course of generations. Professor Jones himself points out that our brains are smaller than those of Neanderthal Man, but that they work in a different way. We are better at making connections, thinking laterally and finding solutions - though not yet to a banking crisis, obviously.

We are also getting ever closer to the science of bioengineering, which would introduce genes into the human body so that people live longer, or become conditioned to resist certain diseases.

This raises the question of how evolution is defined. If, in the face of a global pandemic or some climatic disaster, genetic engineering is used to equip the human race to survive, does that not count as natural selection? Man's ingenuity, in the past, has helped him to survive Ice Ages and flooding, he has adapted to agriculture in place of hunting, developed the ability to digest different kinds of food, built up resistance to diseases that once threatened to destroy the species. Why, then, should he not equip his own body, using the best means available, to help him to survive whatever nature throws at him?

As Charles Darwin himself observed: “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.”

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