A more specific way to put it is, if there actually was some sort of genetic strategy for LGBTQ as a density-dependent response to overpopulation pressures (rather than some simpler default explanation like ‘sex is a large mutational target’ or ‘antagonistic pleiotropy’ or ‘mutation load probably related to evolutionary-recent demographics’), that implies that overpopulation pressures + subsequent LGBTQ response have happened so many times before that a genetic strategy could be repeatedly selected for and refined and blindly evolved. The strategy has to come from somewhere. But the current human population & peak densities are unprecedented and have never happened before. There have not been thousands of cycles of human civilizations arising, developing or failing to develop large LGBTQ subpopulations, and then conquering or being conquered by other civilizations and their fitness decreasing/increasing and subsequent cycles being more likely to have a LGBTQ response. That is just not a thing, and in particular, it is not a thing we see now: LGBTQ percentages are not even positively correlated with country population growth. So such a group selection proposal really does not work.
(One can make a similar observation about the idea of transgenerational epigenetic inheritance having any meaningful impact on human complex traits: …why? Why would evolution build such a complex mechanism to convey a tiny bit of information in a hardwired form instead of relying on the usual within-lifetime learning and adaptation and gene expression? How could any tobacco-specific epigenetic mechanism have arisen? Why would there be a famine/obesity program, since famines arrive frequently and short-term predictably long-term unpredictably, and not without warning once every 30 years like clockwork?)
Update : I didn’t completely get your (gwern) answer at first but after I read eliezer’s post it made more sense, I think I was missing basic information about the topic to fully get it. Your explanation really added something to the original post since it was tailored to the subject I was wondering about.
A more specific way to put it is, if there actually was some sort of genetic strategy for LGBTQ as a density-dependent response to overpopulation pressures (rather than some simpler default explanation like ‘sex is a large mutational target’ or ‘antagonistic pleiotropy’ or ‘mutation load probably related to evolutionary-recent demographics’), that implies that overpopulation pressures + subsequent LGBTQ response have happened so many times before that a genetic strategy could be repeatedly selected for and refined and blindly evolved. The strategy has to come from somewhere. But the current human population & peak densities are unprecedented and have never happened before. There have not been thousands of cycles of human civilizations arising, developing or failing to develop large LGBTQ subpopulations, and then conquering or being conquered by other civilizations and their fitness decreasing/increasing and subsequent cycles being more likely to have a LGBTQ response. That is just not a thing, and in particular, it is not a thing we see now: LGBTQ percentages are not even positively correlated with country population growth. So such a group selection proposal really does not work.
(One can make a similar observation about the idea of transgenerational epigenetic inheritance having any meaningful impact on human complex traits: …why? Why would evolution build such a complex mechanism to convey a tiny bit of information in a hardwired form instead of relying on the usual within-lifetime learning and adaptation and gene expression? How could any tobacco-specific epigenetic mechanism have arisen? Why would there be a famine/obesity program, since famines arrive frequently and short-term predictably long-term unpredictably, and not without warning once every 30 years like clockwork?)
Thanks for the answer and the link ! I’ll go read group selection tomorrow.
Update : I didn’t completely get your (gwern) answer at first but after I read eliezer’s post it made more sense, I think I was missing basic information about the topic to fully get it. Your explanation really added something to the original post since it was tailored to the subject I was wondering about.
Thanks!