missed edit window:
Though it could be, it may not really be a “cultural” effect. I know even some of the simplest of creatures change mating behaviour because of environmental or sexual ratio issues.
Sure, behaviour’s complex. There’s every possibility that a couple might decide to have more kids because Brother Joe is showing no sign of having any of his own - especially if the extended family is pooling resources and so the extra kids are affordable. As I thought I’d been saying all along, a putative homosexuality gene could look at first sight like it would have to be a severe defect from the point of view of the reproductive capability of the individual possessing it, and yet be well able to pass itself along for a whole bunch of reasons.
Indeed. It’s a well-known factoid (I don’t know if the experiment’s been discredited) that rats can turn queer if forcibly overcrowded.
The original subthread was about having enough people to transmit a culture. The fact that absolute rather than per capita numbers are the relevant ones is so blindingly obvious that I thought it would be insulting to spell it out. Evidently I was mistaken.
The downside of proving biological causation is that the anti-gay crowd’s immediate response will be “Great! Now we can get cracking on a genetic cure!”.