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vincentML -> RE: The Religious Right should support gay marriage (1/29/2014 1:34:37 PM)
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quote:
To the best of my knowledge, the only thing that has been established with certainty is that the incidence of male homosexuality has a significant correlation with birth order. The more older male siblings, the higher the probability of homosexuality becomes. And as the hyper-religious tend to have large families, the irony here is that they may be the primary source of the gays they abhor!
A second evolutionary theory about fitness and sexual orientation hypothesizes
that homosexual orientation may increase “fitness” if it prevents
later-born sons of large sibships to engage in unproductive competition
with their older siblings (Miller 2000). The literature suggests some support
for this idea, on first glance. Specifically, a relationship between birth order, or,
more precisely, number of older brothers, and sexual orientation
of males has been reported in a series of papers (Blanchard 1997; Blanchard
and Bogaert 1996a, 1996b; Purcell, Blanchard, and Zucker 2000;
Bogaert 2000). No such effect was found for females. But the evidence
and mechanism proposed are extremely weak. These studies work with
nonrepresentative samples, and/or indirect reports on siblings’ sexual orientation
and suffer from the same biases as noted above in considering
the genetic influence literature. Furthermore, the mechanism by which
such an effect is thought to be activated seems somewhat far-fetched.
Specifically, mothers are hypothesized to carry a “biological memory” (in
the form of an H-Y antigen) of how many sons they have carried, which
leads to changes in the intrauterine environment that activate “feminization
” of younger sons (Blanchard and Klassen 1997; Miller 2000).
In this article, we test the second evolutionary model directly and find
no support for an association between birth-order and same-sex attraction.
Not at all established with certainty.
SOURCE
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