On the causes of sexual orientation

Homosexuality is biological, suggests gay sheep study

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A study of gay sheep appears to confirm the controversial suggestion that there is a biological basis for sexual preference.

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The work shows that rams that prefer male sexual partners had small but distinct differences in a part of the brain called the hypothalamus, when compared with rams that preferred to mate with ewes.

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Kay Larkin and colleagues from Oregon Health and Science University found the difference was in a particular region of the hypothalamus - the preoptic nucleus. The region is generally almost twice as large in rams as in ewes. But in gay rams its size was almost identical to that in "straight" females.

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The hypothalamus is known to control sex hormone release and many types of sexual behaviour. Several other parts of the hypothalamus showed consistent sex differences in size, but only this specific region showed differences that correlated with sexual preference.

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The differences are almost identical to those identified by the neuroscientist Simon LeVay in his studies of the brains of gay men. His work has always been considered controversial, partly because the brains he studied were mostly from men who had died of AIDS. So it was not clear whether the differences were related to the disease or to sexual preferences.

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Hormone converter
But the findings in sheep are an important confirmation of LeVay's work, says Jacques Balthazart from the University of Liege in Belgium.

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Sheep are particularly interesting, he says, because besides humans, they are the only animal where the males may naturally express exclusively gay sexual preferences. As many as one in 10 rams can be gay.

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Larkin's team also found that the hypothalamic region had a rich supply of the enzyme aromatase, which converts testosterone into oestrogen. It is in this form that the hormone interacts with the brain. This may help support one theory that sexual orientation, in part at least, may be related to the hormones present during fetal development, says Balthazart.

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But Larkin suggests there may also be the influence of genes at work, at least in predisposing the animals to homosexuality. This is because selective breeding seems to have been responsible for the high proportion of gay sheep compared with other animals.

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Larkin presented the research on Monday at the Society for Neuroscience meeting in Orlando Florida, US.

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Hoot, we discussed about this at great lengths just last year. Seriously, are you senile? For Sheep, Homosexuality Is In The Genes

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Researchers in the Oregon Health & Science University (OHSU) School of Medicine have confirmed that a male sheep's preference for same-sex partners has biological underpinnings.

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A study published in the journal Endocrinology demonstrates that not only are certain groups of cells different between genders in a part of the sheep brain controlling sexual behavior, but brain anatomy and hormone production may determine whether adult rams prefer other rams over ewes.

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"This particular study, along with others, strongly suggests that sexual preference is biologically determined in animals, and possibly in humans," said the lead author, Charles E. Roselli, professor in the Department of Physiology and Pharmacology. "The hope is that the study of these brain differences will provide clues to the processes involved in the development and regulation of heterosexual, as well as homosexual, behavior."

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The results lend credence to previous studies in humans that described anatomical differences between the brains of heterosexual men and homosexual men, as well as sexually unique versions of the same cluster of brain cells in males and females.

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"Same-sex attraction is widespread across many different species." said Roselli, whose laboratory collaborated with the Department of Animal Sciences at Oregon State University and the USDA Agricultural Research Service's U.S. Sheep Experiment Station in Idaho.

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Kay Larkin, an OHSU electron microscopist who performed laboratory analysis for the study, said scientists now have a marker that points to whether a ram may prefer other rams over ewes.

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"There's a difference in the brain that is correlated with partner preference rather than gender of the animal you're looking at," she said.

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Around 8 percent of domestic rams display preferences for other males as sexual partners. Scientists don't believe it's related to dominance or flock hierarchy; rather, their typical motor pattern for intercourse is merely directed at rams instead of ewes.

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"They're one of the few species that have been systematically studied, so we're able to do very careful and controlled experiments on sheep," Roselli said. "We used rams that had consistently shown exclusive sexual preference for other rams when they were given a choice between rams and ewes."

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OHSU researchers discovered an irregularly shaped, densely packed cluster of nerve cells in the hypothalamus of the sheep brain, which they named the ovine sexually dimorphic nucleus or oSDN because it is a different size in rams than in ewes. The hypothalamus is the part of the brain that controls metabolic activities and reproductive functions.

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The oSDN in rams that preferred females was "significantly" larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase, a substance that converts testosterone to estradiol so the androgen hormone can facilitate typical male sexual behaviors. Aromatase expression was no different between male-oriented rams and ewes.

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The study was the first to demonstrate an association between natural variations in sexual partner preferences and brain structure in nonhuman animals.

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Scientists will work to further characterize the rams' behavior and study when during development these differences arise. "We do have some evidence the nucleus is sexually dimorphic in late gestation," Roselli said.

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They would also like to know whether sexual preferences can be altered by manipulating the prenatal hormone environment, such as by using drugs to prevent the actions of androgen in the fetal sheep brain.

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Born gay? How biology may drive orientation

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As the culture wars rage over gay rights, a flock of sheep at Oregon State University may help answer a key question behind the controversy: Is homosexuality a matter of choice or biology?

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The Corvallis herd includes a group of rams that scientists delicately refer to as "male-oriented." These animals consistently ignore females and bestow all their amorous attentions on members of their own sex.

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Researcher Charles Roselli says a decade of study suggests sexual orientation is largely hard-wired into the sheep's brains before birth. Now, he's trying to figure out how that happens, zeroing in on genes and hormones. In a bold test of his ideas, he hopes to engineer the birth of gay rams by altering conditions in the womb.

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Sheep aren't people, but the Oregon work adds to a growing body of research that bolsters biological explanations for sexual orientation across species ” including humans.

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Despite those scientific findings, some religious groups say homosexuality is a lifestyle that can be treated, if not prevented. One such group, the conservative Christian organization Focus on the Family, is sponsoring a one-day conference in Bothell Saturday.

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The social and political implications of the research are impossible to ignore, leading to unease on both sides of the gay-rights debate. If science proves homosexuality is innate, is there any basis to deny gays equal treatment ” including the right to marry? But if scientists unravel the roots of sexual orientation, will it some day be possible to "fix" people who don't fit the norms or abort fetuses likely to be born gay?

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To the admins:

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Sorry for the long copy and pastes. I had previously discussed this issue with Hoot at least half a dozen times before and he had previously admitted that these researches did indicate that homosexuality is more than just a choice and does have biological basis. However, senility seemed to kick in everytime because he'd always denied having such conversation with me shortly after we had it. I just thought there shouldn't be anymore excuse for him if the articles are posted right on here.

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Sincerely,

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Taz the Baby Eater

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I'm trying to see things your way, but I can't put my head that far up my ass.

After taking out my hand gun and shot the pillow several times, I'm ok now...In science, especially biological and medical, it is considered unethical to study and experiment on humans without having a firm grasp on the controlled and the uncontrolled conditions. So, most of the time researchers have to study animal first before they could move on to human subjects.Don't be intentionally and unreasonably thick-headed, Hoot. You know damn well the implications of studies like these. While there isn't a single "gay gene" like people have suggested in the past, there are certainly combinations of genes that could cause certain prevalent behavioral patterns such as the human sexuality (or more specifically the sexual preference) under certain biological and/or environmental conditions. In other words, bigots like you who have insisted on homosexuality being a choice now have to either acknowledge the implications of the overwhelming evidence for a biological cause.It helps to think of this in terms of computer programming. Some programs may behave slightly different than what the programmer intended. Most of the time, it's not because of a single line of code but rather a combination codes that could form unexpected protocols or subroutines.

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I'm trying to see things your way, but I can't put my head that far up my ass.

No, you along with nem, buzsaw, randman, and a few others have been arguing your heads off that homosexuality is completely a choice. Don't get me wrong. I've not offered definitive proof that homosexuality has biological causes. All I've done is present some evidence that at least tell us the cause(s) for homosexuality is more than just choice.

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I'm trying to see things your way, but I can't put my head that far up my ass.

Anglagard, just remember to be careful about cases like these. We know that dogs hump just about anything when they're horny enough. The only cases (I think) that are supportive of a biological basis for homosexuality are cases of persistent homosexual tendencies even with the presence of members of the opposite sex. For example, there are plenty of chimp and bonobos individuals that only go after other members of their own sex. They just go have sex with other members of the same sex and then go back and help raise their siblings' children. Penguins and geese are other classic examples where they actually would form life-long bonds with members of their own sex. It's been observed that some same-sex goose couples actually would chase away a mother goose to steal her eggs and then rear the young as their own.I swear, the next time I hear a "it's not natural" argument I'm going to scream.

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I'm trying to see things your way, but I can't put my head that far up my ass.

I honestly don't think his intent is to look clever. I just think he wants to be annoying to those of us who take this seriously. After all, nobody is this delusional!

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I'm trying to see things your way, but I can't put my head that far up my ass.