Reddit reviews Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People

Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People https://www.amazon.com/dp/0520240731/ref=cm_sw_r_cp_apa_i_hsJODb3HY1A51

Yes, but with a caveat. Humans are complex creatures. There has been research done in fruit flies where sequences of genes can be switched on and off and cause a preference for one sex or the other.

There is actually a very well researched book called "Evolutions Rainbow" that discusses your question in far greater depth than I could discuss here.

And if you're wondering why those genes don't get selected out (well if gay people don't have kids why are people still gay), it's because the areas that control sexuality aren't one simple on/off toggle switch in humans. So essentially, gay people are created by straight people who pass on the genetic traits for homosexual individuals.

It's also worth pointing out that in addition to sexuality not being a simple toggle switch, the preference for men/women is also fluid. You can look at the Kinsey scale which gives examples of this.

There are people that will identify as entirely straight, entirely gay, people who identify as equally attracted to both sexes, and people who are straight but may be open to encounters with the same sex even if they don't have a strong preference for it.

There's a wonderful book called Evolution's Rainbow by Joan Roughgarden that is entirely about the different genders found in nature. There are several species that have more than one gender like sun fish. (source: that book)