Sexy science: Dishing the dirt is a basic instinct

WOMEN can be real bitches. Mind you, so can men, but when it comes to picking at another's appearance women are the champs. A trawl through the papers as I'm writing reveals, for instance, that Geri Halliwell forgot to shave her armpits, for heaven's sake, Nicollette Sheridan (aka Edie in Desperate Housewives) has knobbly knees, and if Amy Winehouse wants to get the female pundits off her back she really ought to see to her skincare routine.

And the female commentators have got it in for poor old Victoria Beckham, below, just now – she's just got no style, apparently. Mind you, they have got a point. Her massive shades and hoiked-up pseudo-boobs have always looked a bit ridiculous to me. Oh god, look, I'm doing it now! Why do women say such nasty things about each other, especially about the way they look?

Well, it comes down largely to rivalry over men. Bitching is a relatively safe way to bring down the competition. Women tend to be more risk-averse than men and less likely to resort to fisticuffs where they could potentially get disfigured or injured.

We malign others about things we believe the target of our affection values in the opposite sex. This was the finding of a study by evolutionary psychologist David Buss of the University of Texas and his colleagues, who found striking differences in the derogation tactics men and women use.

The researchers found that men tended to denigrate their rival's status, strength and earning power – basically the qualities that women are often most interested in. You know the kind of thing – "what d'you want to be hanging around that loser for, he's a wimp", and so on.

But men, let's face it, are more likely to look for physical attributes when selecting their woman; an hourglass figure and feminine features are indicators of fertility, after all. And naturally, the study found that when women bitched, they usually made fun of others' body size and shape, criticised their rivals' hair and clothes, and pointed out blemishes. And it worked. Men were best able to devalue competitors by disparaging their money-making potential, while women did best by concentrating on physical flaws in their rivals.

But why should a man be less attracted to a woman just because another criticises her appearance? He can see how she looks for himself. For one thing, according to Buss, if a woman spreads around in public her low opinion of her competitor, this could be enough to put him off. Men's social status is affected by how physically attractive his partner is and he is likely to be very sensitive to the views of others on this.

For another thing, making catty comments highlights deficiencies in a rival he might not have noticed. Maybe he didn't clock that flabby tummy or hairy legs, but you can be sure his eagle-eyed partner will have.

We love to dig the dirt with our friends and colleagues, and bitching about a third party can strengthen our own relationships and cement alliances.

Just as our love of gossip translates into a huge appetite for TV soaps, so our natural competitive tendencies make some of us relish sticking the knife in to the stars strutting their stuff in the global village created by celebrity-obsessed media. While most of us are not in direct competition with the rich and famous, it doesn't do our confidence any harm, in these times of airbrushed celebrity gorgeousness, to see some starlet brought down to our level by pointing out her cellulite thighs.

It's unlikely that many of us will get the chance to flutter our eyelashes at David Beckham, after all, although lately he's been getting an eyeful of the nubile Californian cheerleaders at baseball matches he and the wife have been attending.

According to the bitch-mags, this has made Posh anxious and she's been busy trying to make herself look sexier to ward off the competition.

Chances are she's also been making a few snide comments about them in his ear.