Inside our randy genes

THERE are genes controlling our sex drive and promiscuity, says the controversial US scientist whose laboratory identified a "gay gene" in 1993. And, in a new book, Living With Our Genes - Why They Matter More Than You Think, he claims to have identified two of them.

Dean Hamer, a geneticist with the National Cancer Institute in Bethesda, Maryland, says his research team has found a genetic marker for men's willingness to change sexual orientation. It makes "straight" men more willing to try homosexuality and gays more likely to bed women.

The gene in question carries instructions for making a protein which binds to a key chemical transmitter that carries signals between brain cells, the D4 dopamine receptor. One variant of this gene is strongly linked to "novelty-seeking" behaviour - including a willingness to experiment sexually.

As for sex drive, Dr Hamer has found a link between that and different variants of a gene responsible for another protein involved in signalling between brain cells. This one has a key role in transporting serotonin (the chemical targeted by Prozac) inside nerve cells. The thrust of his publicity blurb is that it is almost impossible to underrate the importance of genes in behaviour. But if you hear Dr Hamer debating with his peers, or read the book, it quickly emerges that science is nowhere near knowing how any one gene - or variant - actually controls behaviour.