Current research suggests that homosexuality among men may be caused, at least in part, by hormones encountered in utero. The hormone levels correlate to the number of male children the mother has had. Men who have several older brothers are much more likely to be gay than men who are first-born males.
This could provide a genetic advantage by minimizing fighting among males from the same gene pool, i.e. one is submissive and less likely to compete for dominance, but still available to participate food gathering etc.
Evolution is about the survival of genes, not the survival of a specific organism.
That’s covered in Chapter 7
http://www.mygenes.co.nz/Ch7.pdf
Does Pre-natal Hormonal Exposure
Make You Homosexual?
Summary
Although there are some pre-natal hormonal effects having a major effect on sexual behavior for lower
animals, there is no convincing
evidence for such an effect on sexual orientation in humans. The studies
examining the effects of high doses of female hormones to pregnant women are particularly
informative
because these are very high doses and any hormonal effects on sexual orientation should show up clearly.
But the result is a dubious effect on women and no effects on men. Any effects on sexual orientation appear
to be better explained in terms of gender non-conformity – arguably a psychological construct. Sex drugs do
increase or lower sex drive, but that appears to be about all.
The maternal immune hypothesis is very speculative, and needs much more evidence before it can be
taken seriously.
We leave the last word to several researchers in the field.
“In summary, the evidence from prenatal endocrine
disorders and from the offspring of hormone-treated
pregnancies suggests that hormones may contribute
to, but do not actually determine, the course of sexual
orientation in individuals with an abnormal sexsteroid
history during prenatal life.”3
“At this time, the literature does not support a causal link between hormones
and homosexuality.”10
Men who have several older brothers may find that their mother really wanted a girl and “babies” the youngest.
Same as the “study” that air force pilots have a lot of baby girls (perhaps trying to get a son).
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