Here’s what we know: Homosexuality is normal. Between 2 and 11 percent of human adults report experiencing some homosexual feelings, though the figure varies widely depending on the survey.
Homosexuality exists across cultures and even throughout the animal kingdom, as the authors of a mammoth new review paper on homosexuality write. Between 6 and 10 percent of rams prefer to mount other rams, not ewes. Certain groups of female Japanese monkeys prefer the company of other females:
In certain populations, female Japanese macaques will sometimes choose other females as sexual partners despite the presence of sexually motivated male mates. Female Japanese macaques will even compete intersexually with males for exclusive access to female sexual partners.
Here’s what we don’t know: What, specifically, causes someone to become gay, straight, or something in between. Part of the explanation is genetic, but because most identical twins of gay people are straight, heredity doesn’t explain everything.
The “why” question is important because “there is a strong correlation between beliefs about the origins of sexual orientation and tolerance of non-heterosexuality,” according to the report authors, who are from seven universities spanning the globe. Specifically, people who believe sexual orientation is biological are more likely to favor equal rights for sexual minorities. (When Atlantic contributor Chandler Burr proposed in his 1996 book, A Separate Creation, that people are born gay, Southern Baptists called to boycott Disney films and parks in protest against the publisher, Disney subsidiary Hyperion.) It shouldn’t matter whether people “choose” to be gay, but politically, it does—at least for now.