Homosexuality Again Linked to Biological Factors

[Guest YFSC]

Men with older brothers more likely to be gay

 

By RANDOLPH E. SCHMID, AP Science Writer

 

WASHINGTON - Men who have several older brothers have an increased chance of being gay — whether they were raised together or not — a finding researchers say adds weight to the idea that sexual orientation is based in biology.

 

The increase was seen in men with older brothers from the same mother, but not those who had stepbrothers or adopted brothers who were older.

 

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

 

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.

 

His findings are reported in a paper appearing in Tuesday's issue of Proceedings of the National Academy of Sciences.

 

S. Marc Breedlove, a professor in the neuroscience and psychology department 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.

 

Tim Dailey, a senior fellow at the conservative Center for Marriage and Family Studies disagreed.

 

"We don't believe that there's any biological basis for homosexuality," Dailey said. "We feel the causes are complex but are deeply rooted in early childhood development."

 

There have been a number of attempts to establish a physical basis "and in every case the alleged findings have been severely challenged and questioned," he said.

 

"If it is indeed genetically based it is difficult to see how it could have survived in the gene pool over a period of time," Dailey added.

 

Bogaert said the increase can be detected with one older brother and becomes stronger with three or four or more.

 

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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more links

 

http://news.yahoo.com/s/ap/20060626/ap_on_he_me/sexual_orientation_7

 

http://news.yahoo.com/s/ap/20060626/ap_on_he_me/sexual_orientation_4

 

http://news.yahoo.com/s/hsn/20060626/hl_hsn/homosexualityagainlinkedtobiologicalfactors

[+ Hoover42]

Interesting. Almost all of the sex I had between 10 and 17 was with a group of seven brothers who lived in my neighborhood.

 

I thought they were all straight at the time; I wonder now if many of them were closet cases.

 

...Hoover

[Guest PWIT]

did I miss something? When I first read title, thought the article would be supporting a homosexuality-genetic link. Article seem to support an environmental theory (the environment being the womb). Did I misread?

 

before anyone flame's me, I'm not taking a stand on any side of the issue, just wondering if I am not picking up on something in the article that goes along with the title of the posting.

[+ Charlie]

You misread it. The article claims that there is no statistical link to the environment in which the boys are raised, only to the number of boys which the mother has given birth to. I'm not sure one could consider this a "genetic" link, but rather a biological effect (e.g., a birth defect caused by the mother's exposure to rubella during pregnancy would be biological, but a birth defect passed down on a chromosome would be genetic--I'm not a biologist, so there may be a better way of stating this).

[mansniffing]

I read the story and did chuckle a little thinking about the "intelligent womb." Anything that affirms you don't "choose" being gay is okay by me.

 

In today's news.

 

Women see one color differently than do men: red. She sees crimson, burgundy, and tomato. He sees red. Just plain ol' red. Why? It turns out there's a perfectly good reason why men can't see what is so obvious to women: the many variations--some subtle, some bold--of the color red. Reuters reports that researchers from Arizona State University in Tempe have determined there is a gene that allows us to see the color red, and that gene comes in a high number of variations. Because the gene sits on the X chromosome--and women have two X chromosomes and so two copies of this gene, compared with only one for men--the gene aids women's ability to perceive the red-orange color spectrum. The study findings were reported in the American Journal of Human Genetics.

 

Does this suggest that men who see the variations of red have two X chromosome and not XY? Are they therefore biologically women?

[Guest PWIT]

Thanks Charlie. That helped.

[shy]

i know there are always exceptions; but, i'm a case of the exact opposite of the study. i'm the oldest of four boys, with three sisters also. my three brothers are all married, and i've never had reason to suspect any were the least bit gay.

[Luv2play]

well, I fit the mold perfectly. I had three older brothers and a younger sister. All are straight. Not me though.;-)

[+ Charlie]

We all can think of personal examples and counter-examples, e.g., I have one gay friend who has three older brothers who are straight, but on the other hand my partner is also one of four brothers, and the two older ones are gay but the two younger are straight. The important thing is whether a large scale statistical analysis shows a correlation.