30 Minutes Bay Area

Out At Birth?

(CBS 5) What makes someone gay?

For some it can be a soul-wrenching question. For scientists, it's a chance to understand biology at its most basic level, and perhaps answer an even more profound question - are people born gay?

Ranchers say they've seen it for years, the sheep who just don't seem interested in females. That's a problem for ranchers, because that shyness results in fewer lambs, and less profit.

But when they asked animal researchers for help, the answer was a surprise. It turns out that some of the male sheep aren't shy at all - they're gay.

"We interpret it as a form of homosexuality," says Dr. Chuck Roselli of the Oregon Health & Science University.

Roselli and Fred Stormshak do cutting edge research on what you might call 'gay science' for the University of Oregon.

You may wonder how the scientists know that the rams are gay.

"They are given a choice between two males and two females. We observe their behaviors, and we score them in terms of whether or not they'll mount other males or mount females," Roselli says.

The tests show that about 8 percent of rams are only attracted to other rams. We asked if that meant that there was a gene for homosexuality.

"I don't think there's a gene for homosexuality or heterosexuality, but there are genes for attraction to men or attraction to women," says UCLA geneticist Sven Bocklandt.

Bocklandt says that those attraction genes are usually aimed at he opposite sex, but sometimes get switched to attraction for the same sex.

"The basic attraction -- when someone walks down the street and you turn your head to him or her and say 'Wow!' -- That is very primitive and very simple, and that's what we're trying to understand," Bocklandt says.

UCLA has on of the few labs in the world researching sexual orientation full time. Last month, Bocklandt and Eric Vilain reported that some mothers of gay men show unusual traits in their X-chromosomes, another clue to where those genes may be hiding.

"Sexual attraction is a trait that is so important for us. Wars are fought for love and it makes the world run," Bocklandt says. "All the movies are about it. All the songs are about it. We have no idea how it works."

To help unravel the mystery, scientists are also studying identical twins. We met Brian, who is straight, and his brother Brady, who is gay.

"I remember when I was 13, 14, I went to see that 'Top Gun' movie," recalls Brady. "I'm supposed to be looking at Kelly McGillis, but god! I'm looking at Tom Cruise."

Their mother Donna says that by age three, Brian was very into sports.

"I noticed that Brady stayed in the make-believe kitchen and put on the pink high heels," she says. "I felt like he was gay from the moment he was born."

Twins like Brian and Brady show that genes may be only half of the story. That's because, according to a landmark study, when one twin is gay the other is only gay about half of the time. So if they're identical, why is their sexual orientation different?

Scientists think it has something to do with hormones in the womb.

For example, when scientists give the male hormone testosterone to female finches still in the egg, they grow up acting like males.

In the case of identical twins, their bodies are like houses with matching floor plans. Each light represents a different gene, genes that can be switched on or off by hormones. But hormonal conditions in the womb aren't always the same for each twin. Which means some of their 30,000 genes may get turned on or off differently by altering their brains before they're born.

"There is no genetic--no convincing genetic component to homosexuality," says Dr. Benjamin Kaufman, co-founder of the National Association for Research and Therapy for Homosexuality, or NARTH.

Kaufman is a psychiatrists, and doesn't buy the biological theories. In 1992, Kaufman co-founded NARTH. Most psychologists strongly disagree with NARTH's philosophy that homosexuality can be overcome.

"I consider it a developmental arrest," Dr. Kaufman says. "I have a saying, 'behind every homosexual, every homosexual, is a heterosexual.'"

NARTH criticizes every scientific finding on gay biology, including a 1991 study by brain scientists Simon LeVay. LeVay compared the brains of gay and straight men, focusing on a tiny area in the hypothalamus called INAH-3.

INAH-3 plays a role in sexual attraction and is usually smaller in women than men. LeVay found that INAH-3 is also smaller in gay men compared to straight men -- In other words, more similar to women.

"LeVay's studies were roundly, roundly trashed," Kaufman says. "No one pays much attention to LeVay's studies except those people who want to hold it up as proof of biological homosexuality."

Simon LeVay says his research was attacked because he's a gay scientist, and because some people will never accept that homosexuality may be natural.

"When my work was published in 1991 it was very controversial," LeVay says. "A lot of anti-gay sentiment is invested in the idea that being gay is nothing more than straight people saying to themselves: I think I'll try that gay thing this weekend…The science doesn't support that. The science says that it's not a choice."

When Chuck Roselli cut into the brains of his sheep, he found similar results to LeVay's. Not only do sheep have a brain structure like INAH-3, it's also much smaller in gay rams than straight rams.

"There's no environmental influences that we know of. And there's no choice involved here as far as we know of," Roselli says. "These animals are just doing what their brains and their bodies are telling them what to do."

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