I found this on Youtube the other day, and thought it was pretty interesting.
At time 2:32:
When a woman is pregnant with a boy, scientists are realizing that her female body often sees the male fetus as a foreign object, and begins to produce antibodies against it. The more boys a woman has, the more adept her body becomes at feminizing the fetus which may explain why with every successive boy, the odds that he will be gay go up significantly.
I’m sure I don’t just speak for myself when I say that the standard issue religious talking point of homosexuality somehow being a “lifestyle choice” has been thoroughly unbelievable from the beginning – if not because a group of bible waving fanatics are usually the ones pushing the idea, then because there’s absolutely no science behind it either. Funny how the two are almost always seen together.
To further underscore the sheer incomprehensibility of the claim, one needs to look no further than the Middle East or Africa. I very much doubt that, after thoughtful and careful deliberation, these people would still be willing to make a choice in sexual behavior that would put them at clear and significant risk of getting hanged or stoned by their own government. And that’s only if the angry mobs don’t kill them first.
But yes, I can certainly buy into the idea that while there may be some degree of genetic predisposition to homosexuality, maybe one of the reasons nothing entirely conclusive has yet been drawn from that approach is that there is an equally strong influence of fetal development as a result of the mother’s hormones / environment / health issues.
(To illustrate the point, I was informed recently of a correlation between gender identity disorder in males and the mother’s exposure to a chemical called diethylstilbestrol, which is a synthetic estrogen given to mothers during the 1940s to 1970s to help prevent miscarriage. Thanks again to Tim Kreider for this little gem, if you can believe it. Here are some papers from the doctors who were involved in the studies:)
- Hood E (2005). “Are EDCs blurring issues of gender?”. Environmental Health Perspectives 113 (10): A670–7. doi:10.1289/ehp.113-a670. PMC 1281309. PMID 16203228.
- Blackless M, Besser M, Carr S, Cohen-Kettenis PT, Connolly P, De Sutter P, Diamond M, Di Ceglie D, Higashi Y, Jones L, Kruijver FPM, Martin J, Playdon Z-J, Ralph D, Reed T, Reid R, Reiner WG, Swaab D, Terry T, Wilson P, Wylie K (2006). “Atypical Gender Development – A Review”. International Journal of Transgenderism 9 (1): 29–44. doi:10.1300/J485v09n01_04.
- Rudacille D (2005). The Riddle of Gender (Chapter, “Fear of a Pink Planet”). Pantheon Books. pp. 240–276. ISBN 0-375-42162-9.
- Bao, Ai-Min and Swaab, Dick (2011). “Sexual differentiation of the human brain: Relation to gender identity, sexual orientation and neuropsychiatric disorders”. Frontiers in Neuroendocrinology 32: 214-226.
The take-away from this is that there is documented evidence to support the idea that prenatal exposure to certain hormones will affect the way a person’s brain is wired to determine their gender identity. To make the logical leap that exposure to other groups of hormones could instead influence one’s sexual orientation doesn’t really take a great deal of mental gymnastics, especially in the context of the studies done so far on the topic.
Now, back to the video. I did a little digging, and found some of the papers that explore this hypothesis. Again, this is only something to explain male homosexuality … I don’t know if there’s a decent explanation yet for lesbians, or if they come about by way of a completely different mechanism. Here’s the abstract from a paper called “Fraternal birth order and the maternal immune hypothesis of male homosexuality“:
In men, sexual orientation correlates with an individual’s number of older brothers, each additional older brother increasing the odds of homosexuality by approximately 33%. It has been hypothesized that this fraternal birth order effect reflects the progressive immunization of some mothers to Y-linked minor histocompatibility antigens (H-Y antigens) by each succeeding male fetus and the concomitantly increasing effects of such maternal immunization on the future sexual orientation of each succeeding male fetus. According to this hypothesis, anti-H-Y antibodies produced by the mother pass through the placental barrier to the fetus and affect aspects of sexual differentiation in the fetal brain. This explanation is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring. The maternal immune hypothesis might also explain the recent finding that heterosexual males with older brothers weigh less at birth than heterosexual males with older sisters and homosexual males with older brothers weigh even less than heterosexual males with older brothers.
Again, this is just a hypothesis, so the study of this relationship is, if you’ll forgive the pun, in its infancy. But as the abstract points out, there is quite a bit of corroborating evidence that suggests there is a relationship between the H-Y antigen and sexual orientation in males.
So, the next time some self-proclaimed God Warrio tries to shout you down by telling you that homosexuality is nothing but a choice, you can rest assured that there’s an ever expanding body of evidence that shows otherwise. Religion, on the other hand, is neither genetic nor the result of prenatal exposure to any special hormones. That’s something into which we’re born, but can change on our own at any time. They might want to consider that detail when arguing in favor of restricting rights for people based on what they call “lifestyle choices”.