Paul Vallely: That's me – at the pinnacle of evolution

When Mozart was my age he had been dead two years. Or so Tom Lehrer, that great satirical songster of the early Sixties, said many years ago. Mind you, he didn't go to the gym twice a week, as I do. Mozart, that is. I'm not so sure about Tom Lehrer, though unlike Wolfgang Amadeus, who died at 35, Lehrer was still with us at 83, last time I checked.

So the pecking order goes like this: Mozart, me, then Tom Lehrer. Agewise, that is. All this is important because that makes Mozart young (if dead), me middle aged and Tom Lehrer old. And a book has just come out – a proper book, written by a zoologist, not some feature writer on a women's magazine – that says middle age, which apparently stretches from 40 to 60, represents the human species at the very peak of its powers.

That's me we're talking about.

Mozart, of course, had a hard life, with all that partying and notational scribbling. Too many notes, my dear Mozart, too many notes, as the Emperor Joseph II is supposed to have told him. But then everyone had a hard life in the 18th century before middle age was invented and everyone, by and large, went straight from young to dead often without passing through old.

It's evolution, you see. The Cambridge zoologist David Bainbridge, in Middle Age: A Natural History, says that humans are the only creatures who have a distinct middle age. Most animals, by contrast, carry on breeding until they die. But since it takes up to 20 years for the next generation to grow up and go to university, humans tend to remain healthy for two or three decades after their childbearing potential expires.

Like killer whales (nice company to keep) we follow the unusual practice, Bainbridge says, of sticking with post-menopausal female partners, rather than continually trying to mate with younger models. This makes middle-aged men, apparently, "the most impressive living things yet produced by natural selection" and "the pinnacle of evolution". Ahem.

You might be able to see a number of flaws in this theory as words like monkey gland transplants, old-man-in-sports-car, predatory cougar and dad-dancing suggest. Not to mention specs for short-sightedness, short-term memory loss and getting up in the middle of the night for a wee.

Bainbridge insists all that is outweighed by the repository of wisdom and experience. MRI scans show, he says, that the brain's white matter, which connects the different parts of the brain, actually increases in middle age. Intellectual abilities don't begin to decline until after the age of 65. The middle-aged human brain is the most powerful, flexible-thinking machine in the known universe.

As for the midlife crisis, he insists that is a myth – which is a bit rich from a portly father-of-three who has just bought himself a blue Lotus sports car. (The book must be selling well.) Bainbridge avers this is not a compensatory mechanism prompted by angst about his physical or mental deterioration, or to salve his dawning sense of impending mortality, or to attract young women. It is just that he couldn't afford it before, and now he can.

I had an older friend who thought the same about the big powerful motorbike he lusted after in his youth but lacked the purchasing power to realise in those far-off days. His broken leg is almost better now, thank you. My ambitions were more modest. I tried yoga but it gave me a bad back so I packed it in.

The safest thing, then, is probably to stay at home and open a bottle of Meursault with Mrs Killer Whale. The middle-aged, according to another report in the past few days, get through more alcohol in a steady drizzle over the course of the week than teen binge-drinkers do at their mammoth single sitting. But no one said we were perfect, did they?