TV & Radio
The baffle of the sexes
August 28, 2005 - The Age, Australia
Forget a simple XX or XY - what determines whether it's a boy or a girl is more puzzling than first thought. By Peter Ellingsen.
In some ways it is the most basic question of all. Are you are a man or a woman? For centuries, it seemed simple. Men had male sex organs; women had female ones. This did not do a lot for hermaphrodites, who were born with both, but science seemed to solve the impasse by coming up with a subatomic rather than surface solution: men had XY chromosomes; women had XX chromosomes.
But in the 1990s, researchers, including Melbourne's Dr Andrew Sinclair, in a study of "intersex" people - those with ambiguous genitalia - unearthed a new gene that blew the old certainty out of the water.
Their discovery that a hitherto unknown gene, SRY, was needed to start the process of "maleness" re-opened the gender puzzle. It was now no longer enough to assume that chromosomes defined gender. There was more going on, and while associate professor Sinclair, director of the Royal Children's Hospital molecular-development unit, believes biology will yield the answer, it has not happened yet.
"This is far from simple," he says. "We're just starting to understand what determines gender."
The problem is finding an indisputable dividing line between male and female. It is not the body, as intersex children make clear. One in 2000 of all births involves babies with mixed sex anatomy - often sex organs that are ambiguous - such as a phallus that looks somewhere between a penis and a clitoris, or a divided scrotum that looks more like a labia. Then there are tens of thousands of others with chromosomes that do not comply with the usual XX or XY pattern. Most have normal sex organs and only discover they are different when they try to have children. Are they male or female? The biology does not make it clear.
Melbourne woman Christie North, who was recently featured on a Four Corners program, was born with male chromosomes and testes. Her condition, known as androgen insensitivity syndrome, means her body can generate testosterone, but can't respond to it. She can't have children or menstruate, and receives injections of the female hormone oestrogen to help feminise her body. She looks like a woman and feels and acts like a woman. But if the usual formula for gender - XX or XY chromosomes - were applied she would be considered male. It is confusing. Because her body was unable to process male hormones in the womb, she developed into a female. Hers, as Four Corners noted, is one of more than a dozen intersex conditions that affect thousands of Australians.
Sinclair thinks the solution to the gender puzzle lies in the way testes develop in the embryo. But since his discovery, an answer remains elusive. Talking of the new SRY gene, he says: "We had a very simplistic notion of a linear pathway, but that is just grossly naive," he says. "Fifteen years on we still don't know how it is regulated."
Melbourne colleague, associate professor Vincent Harley, is also investigating the gender question, particularly what the new gene, SRY, might do in the brain. Dr Harley, head of human molecular genetics at Melbourne's Prince Henry's Institute of Medical Research, is trying to understand how the brain may be hard-wired differently for males and females, but does not think something as dramatic as a distinctive male and female gene will be found.
"It comes down to variations in a whole constellation of genes," he says. "I'm not suggesting there's one gene for gender, but I do think there's a biological base for gender identity. There is for everything. Trouble is you will never prove it."
Both experts are optimistic a biological key for gender will emerge, though they acknowledge that the brain's "plasticity" - the way it is hard-wired even after birth by environment - does not rule out a role for nurture. "Plasticity is important," Sinclair says.
This does not mean a return to the 1960s, when nurture was deemed decisive in arriving at the gender of intersex children. Then, spurred on by the theories of New Zealand psychiatrist Dr John Money, surgery was routinely used to assign a sex to a child with ambiguous gender, in the belief that "the psychological sex (would) agree with the haircut".
Psychology, however, is more complex. It is not just that a number of the children surgically assigned a sex grew up to identify with the opposite gender. It is - as a symposium being held in Melbourne this weekend will argue - that sexual preference tends to resist a biological explanation.
A decade ago, US researcher Dean Hamer insisted he had found a "gay" gene. If right, the claim would have provided a genetic marker for sexual desire. But it was wrong, and there are some who now think that attempts to pinpoint the biological origin of sexuality are fraught.
Dr Gary Marcus, associate professor of psychology at New York University, believes, "we're starting to see how, in forming the brain, genes make room for the environment's essential role". He sees the old nature-nurture polarity as false, saying that both interact to create the person. The brain is re-wired, both before and after birth, rather than hard-wired for all time.
Influential author and former Oxford zoologist Matt Ridley agrees. In his new book, Nature via Nurture, he talks of the line between biology and environment being blurred because of the interplay between genes and the outside world.
This is not Sinclair's field, but he senses that sexuality is just as much about "how you feel as how the brain functions". "It's very early days with this," he says.
Harley thinks sexual orientation could be like gender identity, with a complex genetic explanation, perhaps interacting with the environment. "There's stuff going on at both ends, emotions and molecules," he says.
The Royal Children's Hospital's Professor Garry Warne, who treated Christie North, admits he has "no idea" what the marker dividing men and women might be. "There are biological factors but they don't count for 100 per cent," he says. "And I have no idea of what determines sexual preference."
Dr Dany Nobus, senior lecturer in psychology at Britain's Brunel University, has spent more than a decade reviewing sexuality and believes, like the poets, it can't be boiled down to biology. He suggests the most important sexual organ lies between the ears, but not just as genetic particles.
Nobus, keynote speaker at the Australian Centre for Psychoanalysis sexuality symposium today, says you have to include the unconscious. Noting that being a biological male does not automatically trigger a sense of masculinity, he says the body does not determine sexual identity. Nor, he says, does sexual orientation dictate sexual behaviour. This is partly because of the role played by unconscious fantasy.
"A homosexual man with a strong sense of femininity may have heterosexual fantasies in which he occupies the role of a male chauvinist," he says. "Gender is not the whole story of human sexuality. We're dealing with a set of components whose interrelations don't follow any preconceived paths. Human beings are neither purely the playthings of nature, nor simply followers of social forces. Reducing sexuality to nature and nurture reduces human experience."
Dr Dany Nobus will address The Ethics of the New Sexualities symposium at the Treacy Conference Centre, 126 The Avenue, Parkville, at 10am today.