Abstract: Homosexuality is a common occurrence in humans and other species, and yet its genetic basis is poorly understood. It provokes scientists’ interest by contradicting the basic low of natural selection, namely how can a trait that ensures low relative fitness of homosexual individuals compared to heterosexual individuals persist in time. There has been a variety of theories and researches attempting to explain the reasons for the apparently paradoxical existence of this trait, but we still don’t have an all-inclusive theory to explain it. So far we have divided the researches into two main groups: biological, which includes the genetic basis (“fertile females”, “kin selection”, “fraternal birth order” effect,) and the physiological ones (changes in the size of particular parts of the brain, and differences in the hormonal levels of the homosexual and heterosexual individuals); and psychological or also seen as environmental (different theories varying from personal choice, all the way to dramatic early-childhood experience). In this paper I will focus my attention to the genetic basis of the homosexuality and the different theories connected with it.
For human societies at large, homosexuality is a sensitive issue. For biologists it is an intriguing one. How can genes influencing homosexuals, have so non-reproductive behavior, but still be favored by natural selection? Although biologists are still far from answering that question, many possibilities exist. During the past several decades, they have discovered some interesting patterns that may point toward genetic causes of homosexuality. The first groundbreaking research on the genetics of homosexuality was done by a team of geneticists ahead with Dean Hamer in 1993. They reported to have linked “some instances of male homosexuality to a small stretch of DNA on...