Johann Hari: The intriguing tale of the gay sheep

This is the first hard evidence of biological differences between gay and straight mammals

Whatever happens in 2007, we already have the most surreal headline of the year: "Sheep have right to be gay, says Martina Navratilova". But behind this headline and buried beneath the battery of baa-aad jokes it seems to beckon, there is a strange and serious story that will ripple out through the 21st century in ways we cannot predict.

For the past five years, a team of researchers at Orgeon State University has been investigating the sexuality of sheep. Early on, they proved what every sheep farmer knows: some 8 per cent of rams are gay. When it comes to sex, these woolly homosexuals shun ewes and engage exclusively in ram-on-ram action. They will swiftly pounce on any ram stuck in a fence - the sheep equivalent of the prison showers. The gay lovin' on Brokeback Mountain, it turns out, wasn't confined to Jake Gyllenhaal and Heath Ledger.

And it gets more intriguing. When the team studied the brains of these gay sheep, they invariably discovered they have a substantially smaller hypothalamus than their straight male siblings. This is the first hard scientific evidence of biological differences between gay and straight mammals - and they found these brain differences are already in place in the third trimester of pregnancy. Sheep, at least, are born gay or straight.

So what's Martina's problem? It begins with the next stage of the research. It turns out this epidemic of gay sheep is a serious problem for the agricultural industry. This 8 per cent of rams are not breeding, and a further 8 per cent seem to be asexual. (Many of these might be lesbians who can't express their sexuality. Female sheep always express a desire for sex by just standing still. The world's fields may be littered with millions of lesbian sheep lying still, wondering why their dream-ewe never comes). If 16 per cent of your flock is cruising or day-dreaming, that's a lot of lost money.

That's why the experimenters began to try to something new: making the gay sheep straight. They altered the hormonal levels in their brains and monitored their behaviour. And the result? Many of the gay rams decided a bit of ewe wasn't so bad after all. They began to have heterosexual sex.

This experiment throws up difficulties for all sides of the millennia-long debate about homosexuality. It gives the forces of homophobia plenty to fume against by annihilating their most hoary argument: that gay sex is "unnatural". In reality, we live in - as the scientist Bruce Bagemihl puts it - "a polysexual, polygendered world", where species from beetles to shrews to chimpanzees have a consistent minority who prefer their own sex. It's everywhere: cow elephants often masturbate each other with their trunks (why has Sir David Attenborough never shown it to us?) and in the Bronx Zoo there is a famous pair of gay penguins called Wendell and Cass who sit on a little rock they believe is their egg. Human homosexuality is just another example of a universal phenomenon.

The homophobes know that when people realise this, homophobia becomes unsellable. The latest US poll found that 79 per cent of people who think human beings are born gay support full gay equality, while only 22 percent who believe homosexuality is a choice agree. The Family Research Council, an evangelical lobby group in the US, are in a panic. In their latest publication, they warn that discovering people are born gay "would advance the idea that disapproval of homosexuality should be as socially stigmatised as racism". Uh-huh. So they spend hundreds of pages trying to debunk the new evidence.

But the Oregon studies also pose a serious challenge for the supporters of gay rights, like Martina and myself.

At the very moment the world is being forced to admit homosexuality is not a choice, this experiment raises the distant prospect that it might become one after all. Martina sees it as a Mengele moment, raising the spectre of altering the brains of gay people to "cure" them of their "disease". The Oregon scientists can now detect gay sheep in the womb. She fears it is not a great leap to detecting gay foetuses in human wombs, and making possible mass homo-cidal abortions.

There is indeed a horrific history of attempts to "cure" gay people. Alan Turing was perhaps the greatest English genius of the 20th century, breaking the Nazis' codes at Bletchley Park and laying the groundwork for the invention of the personal computer. But when his consensual, loving relationship with another man was discovered, he was given an option: go to prison, or take "hormone therapy". He took the "therapy". He became impotent and grew breasts. After a year, he killed himself.

Today, there are Christian ministries across the world who claim they can "cure" gay people through prayer. A few years ago, I met up with the British branch, and found pitiful, broken men and women soaked in self-hate, invariably "relapsing" into homosexuality and hating themselves even more.

It's not hard to see how a range of violently homophobic rulers from Robert Mugabe to Mahmoud Ahmadinejad would not be sheepish about misusing the idea that hormone injections into the brain can alter sexuality. Even though it's a huge leap from sheep to human sexuality, it could unleash another wave of hellish abuse of gay people.

But is the potential abuse of scientific knowledge a reason not to acquire it, as Navratilova suggests? I'm not so sure. Breakthroughs in ultrasound technology have been used across India and China to stage mass female foeticide, with a drastic fall in girl babies. Does that mean we should have stopped the experiments that led to the discovery of ultrasound?

Some gay people respond that no good can come of these experiments, because they seem designed only for an anti-gay purpose - but that neglects the way scientific breakthroughs occur. Charles Roselli, the Oregon project manager, argues his research could lead to cures for a range of medical conditions that stem from differences in sexual development.

Some black and Asian groups understandably objected to research into the genetic differences between ethnic groups, but they have led to breakthroughs in the investigation of diseases that afflict mainly them, such sickle cell anaemia. The path of scientific progress is jagged; this may well produce advances as well as dangers for gay people.

Yes, like Martina, I fear the consequences of moves to abort or "cure" gay people - but I cannot fear greater knowledge of the biology of human sexuality. We cannot ringfence whole areas from biological investigation because we might not like what we hear, or because lunatics might misuse it. These experiments - and our scientific understanding - must roll on. It's up to us to create the political circumstances in which they will not be abused.

j.hari@independent.co.uk