Men having sex with men

Indian health minister Ghulam Nabi Azad has received a great deal of criticism for saying that gay sex is not only unnatural, but even a disease. Although homosexual intercourse was decriminalized by the Delhi high court in 2009, homophobic attitudes and plain ignorance die hard.

Recently my wife told me about a homophobic incident at our daughter's school in Lelystad. It was toy day, which means that the kids were allowed to bring a toy to play with at school. One of the boys had decided to bring a doll, much to the horror of a dad who had just arrived with his child. He went over to the mother of the boy and told her that it was a very bad idea to let the boy play with dolls because that could turn him gay!

I think homophobic dad and minister Azad should have a chat with brain researcher Dick Swaab who has done extensive research on sexuality and sexual orientation. They would learn about the brain differences (in the hypothalamus) between homosexuals and heterosexuals and they would learn that these brain differences are already determined before birth. It really doesn't matter much what happens to a child after birth; try what you will, you will not change its sexual orientation. In his book Wij zijn ons brein, Swaab also mentions the many unsuccessful ways in which people have tried to "cure" homosexuality: hormonal treatments, castrations, electroshock, epileptic insults, jail time, testis transplants, psychoanalysis, and brain operations. It was all to no avail even though some men under intense social pressure would pretend to be "cured".

What I find interesting about homosexuality is that there is also a strong genetic factor involved. You may wonder how that is possible. Surely natural selection would select against homosexuality if this leads to a reduced number of offspring? Jeremy Yoder recently wrote a really nice piece on this issue on a guest blog at Scientific American. This quote reflects his general idea:

Natural selection causes traits associated with having fewer children to become less common over time. But natural selection is not the only evolutionary process at work in natural populations. Mutation introduces new alleles even as natural selection removes them. Furthermore, the effects of random chance in small populations creates an effect called genetic drift, which can interfere with the expected operation of natural selection.

You really need to read the whole piece to understand what he means though. Yoder backs up his ideas with nice simulations, although they are just intended to clarify his ideas as the actual genetic conditions are likely different. For example, as Yoder himself admits the situation becomes quite different if multiple genes are involved. Indeed, if homosexuality is the effect of interactions between multiple genes then there might not even be selection against the individual genes, especially if they have other positive effects. As indicated by Yoder evidence for a positive effect of genes that cause homosexuality in males comes from the observation that genes that cause homosexuality in males may provide a fitness advantage for females.