June 26, 2006


Men with older brothers more likely to be gay
By RANDOLPH E. SCHMID, Associated Press Writer

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.


brett said...

very interesting, in light of our conversation the other night...

Steve S. said...

two thoughts...

1) Is 900 a large enough sample population when you are dealing with such small percentages?

2) Psychologists (at least in my limited association with them) are continuing to ignore the simple truth that man is more than the sum of his genetic material and his social environment. If this is not true then there is absolutely no conceivable way for man to choose.

This is not to say that 'nature & nurture' are not a monumentally significant portion of what makes up a human being. It only means that 'nature & nurture' are not all that there is to a human being. A human being also possesses a will. This will is not a product of genes and upbringing, but is the 'me' that interacts with the genes and upbringing. Genes and uprbringing are various notes, the will is the melody.

Many of us have never taken the time to learn a melody and so the notes simply come out in discordant chaos. This does not mean that we are incapable of learning the melody.

Sean said...

Jeff J is the youngest of 4.

Mary P. said...

What about men who are the youngest child and all their older siblings are sisters? I had a hard time following this article. If their homosexuality was something from an experience in the womb would that mean that God put it there? Somehow God chemically wired them that way? If this is something that is true then when did it happen? After the fall? So then when people are freed from homosexuality it could be considered a healing, from a chemical imbalance? Then they could prescribe anti-gay drugs and gay people can become straight, like depressed people can become happy?

DeMar said...

If I didn’t know the authors of these notes, I could easily assume they were written by Tom Cruise. And that seems to be the point - except of course, in Sean’s ever so special case of sharing the genealogical make up of his buddy’s nuclear family (a pre postulated outing probability?).
I read a common thread alluding to the incorrectness of homosexuality, and a questioning of the nature of this perceived ill. I wonder how many gay men we all know, and do we look at them as a project to fix as we know them? If the article was about a penchant for jelly donuts, would we have questions regarding the physical predisposition of excessive pastry consumption?
I am chemically and genetically predisposed to addiction, as are many others. My brain chemistry is actually different, in some respects, than those that can partake in moderation. I simply must abstain (and you can be assured this is not through my will alone – but often I feel like I’m the only one around).
So I would ask, is a gay man still sinning if he abstains? And if not, does it matter if the fuzzy nature of the cause is chemical, social, willful, environmental or astral?
Did I just drop that can of worms on the floor?...

Steve S. said...

You're gonna hafta explain the Tom Cruise allusion for me...

As to the allusion to the immorality of homosexuality, I didn't intentionally allude to it, although I have no problem defining sexuality morality in terms of a married man and a married woman. In fact my comments weren't really in any way associated with homosexuality per se. I have had several conversations recently revolving around the psychological profession that have reinforced my belief that psychology (as a general rule) has no slot for a person to exist apart from the genes and the upbringing that they have been handed.

I have never met a man who was openly gay, although I have met several who I perceived to be gay. However, to my knowledge, I have never had a homosexual man who was even an acquaintance. I have had quite a number of friends/acquaintances who were lesbians, oddly enough there is a large lesbian/bisexual population on the Lassen County Community College campus.

As to the causes of homosexuality.

Ultimately I would say that homosexual activity is sin, homosexual affinity is not; however, as persons with decision-making capacities, we are responsible for making decisions that discourage affinity for sinful activity, and refraining from decisions that encourage that activity. This forces us to realize that any individual with a perverted sexual affinity (why should we single out homosexuals, when we could include adulterers, pornographers, etc.) who has made any decisions to encourage that affinity (or omitted decisions that would discourage it) is sinning by doing so; in such a case, their sexual affinity is (at least in part) the result of their own decisions.

As to the brain chemistry...

...latest reseach shows that mental discipline is actually quite potent at changing brain chemistry; it turns out the brain is more like the rest of the body than we realized.

NY Times article

DeMar said...

Affinities, perverted or not, toward sin and the mental discipline to change one's brain chemestry (to some end)...I got to think about that.

Steve S. said...

...I would say any affinity toward sin is, by definition, perverted...