Male Homosexuality & In Utero Influences

This BBC report says that a recent study suggests that the odds of a man being homosexual increase as the number of older brothers increase:

A man's sexual orientation may be determined by conditions in the womb, according to a study.

Previous research had revealed the more older brothers a boy has, the more likely he is to be gay, but the reason for this phenomenon was unknown.

But a Canadian study has shown that the effect is most likely down to biological rather than social factors.

The research is published in the journal of the Proceedings of the National Academy of Sciences.

Professor Anthony Bogaert from Brock University in Ontario, Canada, studied 944 heterosexual and homosexual men with either "biological" brothers, in this case those who share the same mother, or "non-biological" brothers, that is, adopted, step or half siblings.

He found the link between the number of older brothers and homosexuality only existed when the siblings shared the same mother.

The amount of time the individual spent being raised with older brothers did not affect their sexual orientation.

This is an interesting claim, but I do find myself asking some questions.

Bogaert controlled for older brothers with the same biological mother--but I can't tell from this study if he controlled for the presence of the biological father or not.

The absence of biological fathers increases the risk for both boys and girls of molestation, for a complex set of reasons, partly because biological fathers seldom molest their own kids, partly because the same taboos that discourage this are not operating with stepfathers and live-in boyfriend of the week, and partly because children looking for father figures are more likely to look for approval from adult men--and are thus subject to inappropriate advances. We had a babysitter in Irvine whose father was long gone--and this approval seeking from adult men led into a van with a 45 year old who did maintenance work around the complex. This being California, the creep received two years weekend jail time for sexual intercourse with a 13 year old.

Since family size has fallen so dramatically in the last forty years, there are relatively few traditional families anymore that have more than two boys in them. I would suspect that families that have more than two boys in them are disproportionately "blended" families. It is possible that Bogaerts' study is seeing the consequences of increased molestation because of the presence of non-biological fathers in the household.

This previous paper by Bogaert indicates that the male birth order effect is correlated with older brothers only; not the number of siblings, nor with older sisters.

Bogaert's other work doesn't seem very PC. This paper's abstract of which Bogaert is an author shows that there is a correlation between men who go after little boys and men who are interested in other men:

We investigated whether late fraternal birth positions also occur in homosexuals attracted to children or pubescents. Probands were 710 sex offenders from Gebhard et al.''s (1965) study of sexual offending. Homosexual offenders against adults and pubescents had later fraternal birth positions than heterosexual offenders against adults and pubescents, respectively; there was no difference between the homosexual and heterosexual offenders against children. Results provide some evidence that homosexuality in men attracted to immature males is etiologically related to homosexuality in men attracted to mature males.

This other paper's abstract by Bogaert also suggests that homosexuality isn't so different, regardless of whether the intended partner is adult or immature:

The subject's relative attraction to male and female children was assessed by phallometric testing in one analysis, and by his offense history in another. Both methods showed that fraternal birth order correlates with homosexuality in pedophiles, just as it does in men attracted to physically mature partners. Results suggest that fraternal birth order (or the underlying variable it represents) may prove the first identified universal factor in homosexual development. Results also argue against a previous explanation of the high prevalence of homosexuality in pedophiles (25% in this study), namely, that the factors that determine sexual preference in pedophiles are different from those that determine sexual preference in men attracted to adults. An alternative explanation in terms of canalization of development is suggested.

Interesting: 25% of pedophiles are homosexual in the study. Hmmm. Homosexual men are about 3-4% of the population. It does appear that there is a disproportionate number of homosexuals among pedophiles.

There's actually a lot of interesting research this guy Bogaert has published that suggests the possibility that male homosexuality is fundamentally different in its causes than female homosexuality. Male homosexuality may a form of maternal immune system defect that causes the damage and confusion, leading to early puberty and enlarged genitals.