Re: OT: What? the clean-shaven outnumber the bearded?"YerUgly Mug," etc.

Christophe Grandsire wrote at 2003-05-26 10:52:32 (+0200)
 > En réponse à Joe :
 >
 > >   I don't mean to be
 > >derogatory in any way, but I can just see no advantage.
 >
 > There have been enough posts explaining that homosexuality probably
 > was advantageous for the survival of the species as a whole (which
 > is what's important, not the survival of some selected line of
 > individuals). As such, it could be seen as similar to the
 > specialisation of some insect species where 95% of the population
 > is actually sterile. Yet nobody ever claimed it was an evolutionary
 > disadvantage.
 >

I think this is inaccurate.  Natural selection doesn't operate on the
level of the species, or the individual, but the gene.  If a gene
causes altruistic behaviour in an individual (which benefits other
members of the species at the expense of the reproductive fitness of
the individual) then it's maladaptive unless it benefits close
relations (who also carry the gene) more than it benefits competitors.
Eusocial insects don't survive because they benefit their species, but
because they benefit their mothers and siblings.  Due to the
haplodiploid nature of their genetics, they're actually more closely
related to their sisters than would be to their own daughters, so
there's no evolutionary incentive for them to become fertile.

However, I can see a number of ways in which a non-dominant gay gene
could be adaptive:

1)  Having homosexual males around could benefit their relations who
    also carry the gene (females or males carrying it recessively)
    enough to be advantageous.

2)  The gene could be advantageous when co-dominant, like the gene
    which causes sickle-cell anaemia but when co-dominant with another
    allele gives resistance against malaria.

3)  The gene could increase reproductivity when dominant or
    co-dominant in females. (I'm assuming that this gene only causes
    homosexuality in males.)

More probably, some combination of these factors could make such a
gene adaptive.  (Mind you, I don't think genetic factors affecting
sexual orientation in humans are anything like as simple as a single
"gay gene".)

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