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I apologise for the length, but....
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Originally Posted by GlorytoGod
I dont believe this to be true and as far as I know there is no research to back this up.
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There does seem to be some.
From New Scientist:
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Survival of genetic homosexual traits explained
* 00:01 13 October 2004
* NewScientist.com news service
* Andy Coghlan
Italian geneticists may have explained how genes apparently linked to male homosexuality survive, despite gay men seldom having children. Their findings also undermine the theory of a single “gay gene”.
The researchers discovered that women tend to have more children when they inherit the same - as yet unidentified - genetic factors linked to homosexuality in men. This fertility boost more than compensates for the lack of offspring fathered by gay men, and keeps the “gay” genetic factors in circulation.
The findings represent the best explanation yet for the Darwinian paradox presented by homosexuality: it is a genetic dead-end, yet the trait persists generation after generation.
“We have finally solved this paradox,” says Andrea Camperio-Ciani of the University of Padua. “The same factor that influences sexual orientation in males promotes higher fecundity in females.”
Relative differences
Camperio-Ciani's team questioned 98 gay and 100 straight men about their closest relatives - 4600 people in total. They found that female relatives of gay men had more children on average than the female relatives of straight men. But the effect was only seen on their mother’s side of the family.
Mothers of gay men produced an average of 2.7 babies compared with 2.3 born to mothers of straight men. And maternal aunts of gay men had 2.0 babies compared with 1.5 born to the maternal aunts of straight men.
“This is a novel finding," says Simon LeVay, a neuroscientist and commentator on sexuality at Stanford University in California. “We think of it as genes for ‘male homosexuality’, but it might really be genes for sexual attraction to men. These could predispose men towards homosexuality and women towards ‘hyper-heterosexuality’, causing women to have more sex with men and thus have more offspring.”
Camperio-Ciani stresses that whatever the genetic factors are, there is no single gene accounting for his observations. And the tendency of the trait to be passed through the female line backs previous research suggesting that some of the factors involved are on the male “X” chromosome, the only sex chromosome passed down by women. “It’s a combination of something on the X chromosome with other genetic factors on the non-sex chromosomes,” he says.
Immune system
Helen Wallace, of the UK lobby group GeneWatch, welcomes the new research that moves away from the controversial single-gene theory for homosexuality. “But it’s worth noting that the data on the sexuality of family members may be unreliable, so more studies are likely to be needed to confirm these findings,” she says.
Even if the maternal factors identified by Camperio-Ciani’s team are linked with male homosexuality, the research team’s calculations suggest they account for only about 14% of the incidence.
Their findings also support earlier findings that when mothers have several sons, the younger ones are progressively more likely to be gay. This might be due to effects changes to the mother’s immune system with each son they carry.
But Camperio-Ciani calculates the contribution of this effect to male homosexuality at 7% at most. So together, he says, the “maternal” and “immune” effects only account for 21% of male homosexuality, leaving 79% of the causation still a mystery.
This leaves a major role for environmental factors, or perhaps more genetic factors. “Genes must develop in an environment, so if the environment changes, genes go in a new direction,” he says. “Our findings are only one piece in a much larger puzzle on the nature of human sexuality.”
Journal reference: Proceedings of the Royal Society B: Biological Sciences (DOI: 10.1098/rspb.2004)
Survival of genetic homosexual traits explained - being-human - 13 October 2004 - New Scientist
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From the BBC:
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How homosexuality is 'inherited'
Scientists say they have shown how male homosexuality could be passed from generation to generation.
Nature encourages mothers to pass on a "gay trait" to their male offspring by boosting their fertility, the Italian University of Padova team believes.
This would keep the pattern of gay inheritance alive, they told the Royal Society's Biological Sciences journal.
Critics of the theory argue a gay gene would eventually be wiped out because gay couples do not procreate.
Inheritance theory
There is controversy about whether sexual orientation is a matter of choice, the authors of the study admitted to the journal.
Campaigners say equality for homosexual people is the more important issue.
Back in 1993, US researchers suggested male homosexuality was passed from mother to son after they found strong patterns of inheritance in family trees.
There might be...reproductive advantages associated with male homosexuality.
The study authors
It has also been noted that homosexual males are more often the younger siblings of a number of older brothers.
Scientists have said it might be that the mother develops some kind of resistance to the male Y chromosome in her offspring that makes subsequent baby boys more likely to be born gay.
Scientists doing DNA studies on homosexual brothers pinpointed 'culprit' genetic material to a region of the X chromosome that mothers pass on to their offspring.
But other researchers in the US have not been able to replicate these findings.
Highly fertile
Andrea Camperio-Ciani and colleagues argue genetic factors favouring homosexual male offspring could make women more fertile.
"Our data resolve this paradox by showing that there might be, hitherto unsuspected, reproductive advantages associated with male homosexuality," they said.
They looked at 98 homosexual and 100 heterosexual men and their relatives, which included more than 4,600 people overall.
The female relatives on the mother's side of the homosexual men tended to have more offspring than the female relatives on the father's side.
This suggests that these women who, in theory, pass on the gay trait to their male offspring are also more fertile.
In comparison, the female relatives on both the mother's and the father's side of the heterosexual men did not appear to be as fertile, having fewer offspring.
The researchers believe the homosexuality-increased fertility trait must be passed down on the female X chromosome.
They pointed out that this would not explain the majority (80%) of cases, and that cultural factors might be important.
Bigger picture
"It is clear that our findings, if confirmed by further research, are only one piece in a much larger puzzle on the nature of human sexuality," they said.
In 2002, the Nuffield Council on Bioethics produced a report into the possible link between genes and behaviour, which included sexual orientation.
It concluded: "There are numerous problems with genetic and other biological research into sexual orientation which mean that any reported findings must be viewed with caution."
It said many of the genetic studies were too small to draw definite conclusions from.
Alan Wardle from the gay rights charity Stonewall said: "This is an interesting debate and there may well be a genetic element, but it's not conclusive.
"It does not really matter whether it is nature or nurture.
"The important thing is getting equality for homosexual people."
BBC NEWS | Health | How homosexuality is 'inherited'
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From New Scientist again:
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Homosexuality is biological, suggests gay sheep study
* 10:51 05 November 2002
* NewScientist.com news service
* Helen Phillips, Orlando
A study of gay sheep appears to confirm the controversial suggestion that there is a biological basis for sexual preference.
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.
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.
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.
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.
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.
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.
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.
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.
Larkin presented the research on Monday at the Society for Neuroscience meeting in Orlando Florida, US.
Homosexuality is biological, suggests gay sheep study - 05 November 2002 - New Scientist
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