I have been following this interesting thread for a while,
so here's my 2 cents.
If the paper in Science a couple of years ago about chromosomal
assignment turns out to be correct, the "gay" gene is on the
X-chromosome. If so, the switch gene must have adaptive value
for females and not males. A female with the gene of interest would
have a counterbalancing normal gene under most circumstances. If
she were homozygous, then I guess she couldn't be a normal
heterosexual. What adaptive value might this be for women?
To achieve the Darwinian objective of spraying out their genes as far as
possible, some authorities note that men tend to be promiscuous.
However, since women have limited reproductive opportunities because
of the duration of pregnancy, their strategy has to be one of
choosing wisely among candidate mates to maximize the opportunity
for their offspring to survive among the fittest. Thus, a switch
gene that allows women to be "bi" and thus less inclined to be
promiscuous might confer the evolutionary advantage that has been
the subject of this thread.
Just a little hypothesis...
E-mail: mdt1 at columbia.edu
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