Well I've found this very interesting article:
What makes people gay?
Researchers may never locate a 'gay gene.' But according to The
With crystal-blue eyes, wavy hair, and freshly scrubbed faces, the boys look as though they stepped out of a Pottery Barn Kids catalogue. They are 7-year-old twins. I'll call them Thomas and Patrick; their parents agreed to let me meet the boys as long as I didn't use their real names.
Spend five seconds with them, and there can be no doubt that they are identical twins—so identical even they can't tell each other apart in photographs. Spend five minutes with them, and their profound differences begin to emerge.
Patrick is social, thoughtful, attentive. He repeatedly addresses me by name. Thomas is physical, spontaneous, a bit distracted. Just minutes after meeting me, he finds a reason to punch me in the upper arm. It's a hard punch. The twins horse around like typical brothers, but Patrick's punches are less forceful and his voice is higher. The differences are subtle, but they are there. When the twins were 3, Thomas blurted out that toy guns were his favorite things. Patrick piped up that his were the Barbie dolls he discovered at day care. When the twins were 5, Thomas wanted to be a monster for Halloween. Patrick said he was going to be a princess.
Their mother—intelligent, warm, and open-minded—found herself conflicted. She wanted Patrick—whose playmates have always been girls—to be himself, but she worried his feminine behavior would expose him to ridicule. She decided to allow him free expression at home while setting some limits in public. That approach worked until last year, when a school official called to say Patrick was making his classmates uncomfortable. He kept insisting that he was a girl.
Patrick exhibits behavior called childhood gender nonconformity, or CGN. This doesn't describe a boy who has a doll somewhere in his toy collection or tried on his sister's Snow White outfit once, but rather one who consistently exhibits a host of strongly feminine traits and interests while avoiding boy-typical behavior like rough-and-tumble play. There's been considerable research into this phenomenon, particularly in males. The data suggest there is a good chance Patrick will grow up to be homosexual. Not all homosexual men show this extremely feminine behavior as young boys. But of the boys who do exhibit CGN, about 75 percent of them turn out to be gay or bisexual.
What makes the case of Patrick and Thomas so fascinating is that it calls into question both of the dominant theories in the long-running debate over what makes people gay: nature or nurture, genes or learned behavior. As identical twins, Patrick and Thomas began as genetic clones. From the moment they came out of their mother's womb, their environment was about as close to identical as possible—being fed, changed, and plopped into their car seats the same way, having similar relationships with the same nurturing father and mother. Yet before either boy could talk, one showed highly feminine traits while the other appeared to be "all boy."
"That my sons were different the second they were born, there is no question about it," says the twins' mother.
So what happened between their identical genetic starting point and their births? They spent nine months in utero. In the hunt for what causes people to be gay or straight, that's now the most interesting and potentially enlightening frontier.
For much of the 20th century, the dominant thinking connected homosexuality to upbringing. Sigmund Freud speculated that overprotective mothers and distant fathers helped make boys gay. It took the American Psychiatric Association until 1973 to remove "homosexuality" from its manual of mental disorders.
Then, in 1991, a neuroscientist in
Later that same year,
In 1993 came the biggest news: Dean Hamer's discovery of the "gay gene." In fact, Hamer, a researcher at the National Cancer Institute, hadn't quite put it that boldly or imprecisely. He found that gay brothers shared a specific region of the X chromosome, called Xq28, at a higher rate than gay men shared with their straight brothers. Hamer suggested this finding would eventually transform our understanding of sexual orientation.
That hasn't happened yet. But the clear focus of sexual-orientation research has shifted to biological causes, and there hasn't been much science produced to support the old theories tying homosexuality to upbringing.
As a 21-year-old college junior lies inside an MRI machine, she manipulates controls that allow her to indicate strong "likes" or "dislikes" of what she's seeing. Hundreds of pornographic images—in male-male and female-female pairings—flash before her eyes. Regardless of which buttons the student chooses to press, though, the MRI scans show her arousal level to each image, at its starting point in the brain.
"I'm not suggesting that most women are bisexual," says Michael Bailey, the psychology professor whose lab conducted the studies. "I'm suggesting that whatever a woman's sexual arousal pattern is, it has little to do with her sexual orientation." That's fundamentally different from men. "In men, arousal is orientation. It's as simple as that. That's how gay men learn they are gay."
These studies mark a return to basics for the 47-year-old Bailey. He says researchers need a far deeper understanding of what sexual orientation is before they can determine where it comes from. Female sexual orientation is particularly foggy, he says, because so little research has been done.
But let's get back to Thomas and Patrick. Because it's unclear why twin brothers with identical genetic starting points and similar post-birth environments would take such divergent paths, it's helpful to return to the beginning.
Males and females have a fundamental genetic difference—females have two X chromosomes, and males have an X and a Y. Still, right after conception, it's hard to tell male and female zygotes apart, except for that tucked-away chromosomal difference. Normally, the changes take shape at a key point of fetal development, when the male brain is masculinized by sex hormones. The female brain is the default. The brain will stay on the female path as long as it is protected from exposure to hormones. The hormonal theory of homosexuality holds that, just as exposure to circulating sex hormones determines whether a fetus will be male or female, such exposure must also influence sexual orientation.
The cases of children born with disorders of "sexual differentiation" offer insight. William Reiner, a psychiatrist and urologist with the
Sexual orientation, Reiner says, seems to be set before the sexual organs are formed. But he also says that exposure to sex hormones probably does not provide the complete answer. More likely, hormones are interacting with other factors.
Canadian researchers have documented a "big-brother effect," finding that the chances of a boy being gay increase with each additional older brother he has. So, a male with three older brothers is three times more likely to be gay than one with no older brothers. They argue that this results from a complex interaction involving hormones, antigens, and the mother's immune system.
There is, in any case, substantial evidence showing correlation between sexual orientation and traits that are set when a baby is in the womb. Take finger length. In general, men have shorter index fingers in relation to their ring fingers; in women, the lengths are generally about the same. Researchers have found that lesbians generally have ratios closer to those of males. Other studies have shown masculinized results for lesbians in inner-ear functions and eye-blink reactions to loud noises, and feminized patterns for gay men on certain cognitive tasks like remembering the placement of objects.
Considering the case of the twins,
Genes could be involved in the process, but, at the
According to Bocklandt, it's not a question of what genes you have, but which ones you use. "I have the genes in my body to make a vagina and carry a baby," he says. "But I don't use them, because I am a man."
Vilain and Bocklandt are also testing an intriguing theory involving imprinted genes. Normally, we each have two identical copies of every gene, one from each parent. But an imprinted gene is a copy that is blocked from working, and the coding that keeps an imprinted gene shut down can vary between identical twins.
As researchers continue the hunt for the basis of sexual orientation, the mother of twins Patrick and Thomas has come to her own conclusions. She says Patrick's feminine behavior suggests he will grow up to be gay, and she has no problem with that.
She just worries about what happens to him between now and then.
After that fateful call from Patrick's school, she says, she "had no clue" how to counsel her son, but decided to tell him that although he could continue playing however he wanted at home, he had to stop telling his classmates he was a girl.
She asked him, "Do you think that you can convince yourself that you are a boy?"
"Yes, Mom," he said. "It's going to be like when I was trying to learn to read, and one day I opened a book and I could read."
At that, his mother's heart sank. She could tell that he wanted more than anything to please her. "Basically, he was saying there must be a miracle—that one day I wake up and I'm a boy. That's the only way he could imagine it could happen."
©2005 by The
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