Darling, your body's so evenly matched

"Hi, my name's David. Can I buy you a drink? I may look pretty ordinary with my clothes on, but underneath baby, I'm ... symmetrical." At this point any rational woman should sit herself down, smile and begin to plan where the reception will be held. She now knows all that is necessary - for something called "body symmetry" is not only a pleasing thing to the eye, but a crucial indicator of the intelligence, reproductive ability and even the love-making skills of any man.

This is why, a few days ago, a Dr John Manning of Liverpool University announced yet another study - this one funded by the hugely important Wellcome Trust - into the role of "cyclical asymmetry" on hormonal changes. Dr Manning already knows enough to assert that animals that are very symmetrical "live longer, run faster and are more attractive to the opposite sex". And this is not just because a dog, say, with legs only on one side of its body has difficulty keeping up with the pack, or balancing itself during copulation. It is actually down to the correlation between symmetry and healthy genes.

At this point I call upon the expertise of Professor Randy Thornhill of the University of New Mexico. Professor Thornhill, or Randy, as I shall call him, measured the fingers, wrists, elbows, ankles and feet of 250 New Mexican students (not to be confused with new Mexican students). What he discovered was that the more "symmetrical" men had more sexual partners and gave their lovers more orgasms. Symms invoked climaxes 75 per cent of the time (while making love, I presume), whereas asymmetricals managed a hit rate of only 30 per cent. I suspect that many New Mexican women students have been wondering how they have only ever managed to sleep with asymmetrical males. And, as if this wasn't enough, Randy also found out that symms actually produced more sperm than asymms.

It is true that much of the evidence from the animal kingdom comes from a study of the Japanese scorpion fly, where the female is attracted to the male with the most symmetrical wings. And it is a shame that no studies have been done in animals a little closer to Homo sapiens than the scorpion fly, like, er, just about anything. But, if you think about it, some of it makes sense anyway. A chap can have two perfect, limpid blue eyes, but if one is a foot lower than the other, the effect is somewhat spoiled.

Randy thinks that symmetry is an "evolutionary genetic marker" and that its degree "shows how well an individual's genes deal with the insults that life hands out". Those whose genes have handled things badly begin to go all lopsided, while those with better genes do not.

This is, in many ways, rather counter-intuitive (if not unwelcome). Symmetry, as I understand it, means to be exactly the same on the left-hand side as on the right, except mirrored (it wouldn't be symmetrical to have two identical left-hand sides of one's body tacked together, with a bit of liver, say, resting on a hip). Symmetry doesn't mean, either, to be the same above the waist as below. Unless one was being scrutinised by something sitting on a vertical plane.

But if this is genuinely the test, then you could be a stick insect look- alike, or a steatopygous rhino type, and still be immensely attractive - just so long as you were exactly as skinny or obese on one side as on the other. In fact a big, fat, totally symmetrical bloke could be considered more beautiful than Michelangelo's David, who is - in one tiny but crucial respect - lopsided.

So I predict that when this unexpected message finally sinks in, there are going to be some fairly profound consequences. Cosmetic surgery will stop being about bulk and reduction, and become a matter of injecting new balance. "Bigger, smaller, who cares? Just make 'em the same!" customers will cry. Size really won't matter, but bend certainly will. Men, when asked on which side they dress, will indignantly tell their tailors that it "hangs straight down the middle," and Turkish drop-crotch trousers will be very much in vogue. New-born babies will be scrutinised for signs of differential droop; insurance companies will ask prospective policy- holders for measurements of symmetry or degrees of deviation, and actors will never, ever claim that this is their "good side".

Culture, too, will change. We will hear no more the old La Rochefoucauld saw about true beauty being flawed. Instead Jackie Collins novels will record intimate and passionate discussions, including lines such as "Darling, darling I love your wrists. They're so similar," and, "Your breasts are perfect. I've just weighed them and they're exactly 2.75 kilos each."