An ageing male flaunting a new Porsche may be the butt of derisive male jokes. But he is far more likely to entice female mates than a younger man with a similar sports car.
That is the surprising conclusion of zoologists who believe they have discovered the secret of one of society's most baffling mysteries: the phenomenon by which older males attract young female mates.
It is, says zoologist Stephen Proulx, a matter of genetic strength. 'If males can display ostentatiously at that age then they really have to have something going for them,' he told The Observer .
The theory therefore provides a new answer to the question: 'What on earth does she see in him?' In the past, it was assumed wealth was the key. As the saying ran: 'Girls like a man with a past but prefer one with a present.' Or as Caroline Aherne once asked Debbie Magee: 'So what first attracted you to the millionaire Paul Daniels?'
However, such interpretations do not explain why gold-diggers are nearly always female and why sugar parents are nearly always male. Why not the other way round?
To get round this problem, scientists argued instead that the Woody Allens, André Previns, and Michael Douglases of the world make ladies flush simply because they are still around to look attractive. Their senior years display how strong are their genes. In other words, in our evolutionary past, when people generally pegged it in their twenties, the fact that a man made it to his sixties indicated he must have something very powerful going for him genetically, a trend that still produces biological effects.
Similarly, the reverse process - younger males seeking older females - occurs far more rarely because a woman's fertility starts to decline in her mid-thirties, and terminates in the menopause, researchers added.
However, the idea has been criticised because it does not explain why young women are not attracted to all older men. As a result, Proulx has put forward new findings in the Proceedings of the Royal Society - a theory that combines both the ideas of wealth and male longevity. It is the very fact that an older male can still display his munificence that really makes a female's head turn. A younger male may do so, but a potential mate does not know how long he is capable of maintaining that ostentation. It could be all over too quickly.
In other words, any stag that can still display a fine set of antlers in the twilight of its years, or an old peacock that can still rustle up a first-rate plumage - or an ageing Lothario who can still sport a Rolex and a riverside apartment - has to be considered a major catch. Only a creature with really powerful genes can do that and therefore attract females who are, in general, the ones who choose partners while males wait to be selected.
Proulx's theory is based on studies of the collared flycatcher and the three-spined stickleback. 'When malnourished these animals still make extreme efforts to display and attract females,' said Proulx, a zoologist at the University of Oregon. 'Such display cost them dearly in expenditure of energy, however, and are only done to attract females before the weakened male has a chance to die.
'The female has to work out if the male is wasting all this energy and is trading in long-term survival for short-term mating success. However, if she can pick an old male who can still display she knows she is onto a good thing.
'It is the equivalent of a young guy not blowing his cash on a sports car to catch girls, but being careful with his money until his sixties when he can start to spend it on Armani suits and Harley Davidsons. Such displays, in the elderly, are unconsciously reassuring to women.'
It is an intriguing argument, as Steve Jones, the geneticist and author of Y: The Descent of Men, acknowledges. 'This sounds a particularly sophisticated sociobiological argument, though that is not necessarily a compliment, for sociobiological theories tend to disappear into gaseous vapour when you think about them for a while. They are scientific just-so stories that you can use to explain almost every human attribute - from acne to zoophilia.'