Men With Older Brothers More Likely to be Gay -
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post #1 of 58 (permalink) Old Jun 26th, 2006, 05:05 PM Thread Starter
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Men With Older Brothers More Likely to be Gay

Men with older brothers more likely to be gay


WASHINGTON - Having several older brothers increases the likelihood of a man being gay, a finding researchers say adds weight to the idea that there is a biological basis for sexual orientation.

"It's likely to be a prenatal effect," said Anthony F. Bogaert of Brock University in St. Catharines, Canada, "This and other studies suggest that there is probably a biological basis for" homosexuality.

S. Marc Breedlove of Michigan State University said the finding "absolutely" confirms a physical basis.

"Anybody's first guess would have been that the older brothers were having an effect socially, but this data doesn't support that," Breedlove said in a telephone interview.

The only link between the brothers is the mother and so the effect has to be through the mother, especially since stepbrothers didn't have the effect, said Breedlove, who was not part of the research.

Bogaert studied four groups of Canadian men, a total of 944 people, analyzing the number of brothers and sisters each had, whether or not they lived with those siblings and whether the siblings were related by blood or adopted.

He reports in a paper appearing in Tuesday's issue of Proceedings of the National Academy of Sciences that having several biological older brothers increased the chance of a man being gay.

It's an effect that can be detected with one older brother and becomes stronger with three or four or more, Bogaert said in a telephone interview.

But, he added, this needs to be looked at in context of the overall rate of homosexuality in men, which he suggested is about 3 percent. With several older brothers the rate may increase from 3 percent to 5 percent, he said, but that still means 95 percent of men with several older brothers are heterosexual.

The effect of birth order on male homosexuality has been reported previously but Bogaert's work is the first designed to rule out social or environmental effects.

Bogaert said he concluded the effect was biological by comparing men with biological brothers to those with brothers to whom they were not biologically related.

The increase in the likelihood of being gay was seen only in those whose brothers had the same mothers, whether they were raised together or not, he said.

Men raised with several older step- or adopted brothers do not have an increased chance of being gay.

"So what that means is that the environment a person is raised in really makes not much difference," he said.

What makes a difference, he said, is having older brothers who shared the same womb and gestational experience, suggesting the difference is because of "some sort of prenatal factor."

One possibility, he suggests, is a maternal immune response to succeeding male fetuses. The mother may react to a male fetus as foreign but not to a female fetus because the mother is also female.

It might be like the maternal immune response that can occur when a mother has Rh-negative blood but her fetus has Rh-positive blood. Without treatment, the mother can develop antibodies that may attack the fetus during future pregnancies.

Whether that's what is happening remains to be seen, but it is a provocative hypothesis, said a commentary by Breedlove, David A. Puts and Cynthia L. Jordan, all of Michigan State.

The research was funded by the Social Sciences and Humanities Research Council of Canada.


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post #2 of 58 (permalink) Old Jun 26th, 2006, 05:26 PM
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I don't have a brother and only have two older sisters yet I'm still gay

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post #3 of 58 (permalink) Old Jun 26th, 2006, 05:29 PM
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I'm an only child...and gay.

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post #4 of 58 (permalink) Old Jun 26th, 2006, 08:46 PM
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3 % i thought it was 10 %
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post #5 of 58 (permalink) Old Jun 26th, 2006, 08:58 PM
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It's true in my family. My youngest brother is gay, he's got two older brothers.

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post #6 of 58 (permalink) Old Jun 26th, 2006, 09:05 PM
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I have read another study done in Italy that said women who have gay sons are more fertile and therefore produce more offspring, this would point to the elder brother being gay.


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post #7 of 58 (permalink) Old Jun 26th, 2006, 11:31 PM
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...this study or similar has been done before.
Interesting that the focus is on gay men only.

I am the oldest though...

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post #8 of 58 (permalink) Old Jun 26th, 2006, 11:44 PM
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Originally Posted by bionic71
...this study or similar has been done before.
Interesting that the focus is on gay men only.

I am the oldest though...
I've posted the New Scientist article before...twice.
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post #9 of 58 (permalink) Old Jun 27th, 2006, 12:10 AM
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Well i have an older brother... so it could be right!

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post #10 of 58 (permalink) Old Jun 27th, 2006, 12:12 AM
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Originally Posted by jmd
3 % i thought it was 10 %
It's probably more than 10%.
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post #11 of 58 (permalink) Old Jun 27th, 2006, 12:16 AM
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I have a older brother

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post #12 of 58 (permalink) Old Jun 27th, 2006, 01:21 AM
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almost every study I've read about being gay has been an absolute heap of cock!

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post #13 of 58 (permalink) Old Jun 27th, 2006, 01:23 AM
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I have an older bro
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post #14 of 58 (permalink) Old Jun 27th, 2006, 01:31 AM
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i guess in a darwinian sense it could have validity --- the oldest have the better chance of survival, so the youngest is gay to increase the chances of the older siblings to reproduce. i'm not sure if i buy it though.

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post #15 of 58 (permalink) Old Jun 27th, 2006, 01:59 AM
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OMG, I have an older brother

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