Evolutionary biologist Bryan Gitschlag discusses what is and is not known about the biology of homosexual orientation.
LINKS FOR FURTHER READING
Here is Bryan’s twitter thread (worth bookmarking)
Homophobia & heteronormativity largely stem from a feeling that homosexuality is “unnatural.” The obvious counterpoints—that it occurs in cultures all around the world, and in other species, and that it’s partially heritable—invite the question: what explains its persistence? ?
— Bryan Gitschlag (@BryanGitschlag) November 17, 2022
This paper shows there is not “A” gay gene, but that there are many genes (mutations/alleles) that influence sexual orientation: https://www.science.org/doi/10.1126/science.aat7693
This paper is one of many talking about evidence for the “antagonistic” hypothesis – the idea that a single gene can multiple unrelated effects (pleiotropy) and that some genes influencing homosexuality in men, have very different effects in women – the genes increase a woman’s chances of having multiple offspring: https://www.nature.com/articles/s41562-021-01168-8
This paper studies the antagonistic hypothesis in fruit flies (it’s found in them too!): https://royalsocietypublishing.org/doi/10.1098/rspb.2015.0429
This paper is a survey of the prevalence of homosexual orientation across cultures: https://link.springer.com/content/pdf/10.1007/s10508-019-01590-0.pdf?pdf=button
This paper reviews many studies on homosexual behavior (not necessarily orientation) in non-human animals: http://www.faculty.ucr.edu/~mzuk/Bailey%20and%20Zuk%202009%20Same%20sex%20behaviour.pdf