Gayness

Over on Language Log, in a another post about how popular science journals, in this case the New Scientist, can't ever get the science right (the journal is claiming that gayness is determined at birth and we can see this because gay guys' brains are wired like girl brains and lesbian brains are wired like boy brains, and Zwicky has his doubts.)

But the point I want to get to is a fella in the comments who suggests, as many of my earnest students have suggested, thinking they are scoring points with me, the liberal professor who obviously has swallowed that Darwinism stuff hook-line-and-sinker, that gayness can't be genetic, now, can it? Or it would have died out! Generations ago!

...if homosexuality is determined genetically, wouldn't it, according to the Mendelian theory of genetics, disappear after a single generation, since only heterosexual couples can reproduce? Even if we take cultural pressure into consideration, there's no way that homosexuality, being documented as early as (if not earlier than) the Old Testament references to Sodom and Gomorrah (the former being the root of "sodomy"), could have survived this long unless it's an experientially gained trait.

(His inclusion of Sodom and Gomorroh, here, for me, tips his hat -- boy is not arguing in good faith, in my opinion, or that would not be the historical reference that leapt to his mind.)

Anyway, another commenter replied thus:

1. Recessive genes.
2. Inclusive fitness.
3. The ability to have sex with a partner capable of producing offspring even if we don't enjoy it very much.
Developmental biology presents other possibilities.

Which leads us to PZ Meyers, which is so why I like the blogosphere.

I can think of quite a few hypothetical mechanisms that would drive the prevalence of homosexuality. They could every one be true, and just postulating or even providing conclusive evidence for a mechanism doesn't mean all the other mechanisms are false. I'll list a few ideas: none are contrary to evolutionary thinking.

Then he goes on to list them...well, I won't, since he does. But it's great.

And none of them have anything to do with wicked sinners and a vengeaful God.

Well, d'oh.