Physics is not the only science, biology is a science, too.
Scientists at the University of Padua, Italy, studied the genetic components of homosexuality.
Andrea Camperio Ciani and his team did not quite make a hard biological experiment; it was rather a poll of 98 homosexuals and 100 heterosexuals, including 4,600 of their relatives.
Nevertheless the outcome seems to be that homosexuality is contained in a gene associated to the X chromosome. Recall that women have XX while men have XY, which means that his Y must be inherited from the father, and consequently his X must be inherited from the mother.
In other words, homosexuality of men is inherited purely from the mother.
The Italian statistical analysis showed that homosexuality was correlated with homosexuality of other relatives. More importantly, it has shown that that mothers and aunties of homosexuals were more fertile (something like 2 vs. 1.5 daughters and sons).
If one believes these results, the homosexual gene is carried both by men and women, and it causes homosexuality of men, and hyper-heterosexuality (or fertility) of women. This trivially resolves the well-known paradox due to Darwin why don't the homosexual genes disappear: the women compensate for the men.
This Italian work is not quite original. The American genetician Dean Hamer announced in 1993 that he had found a gene Xq28 on the X chromosome that was supposed to be responsible for homosexuality. However, his statements were not quite confirmed.
Camperio Ciani argues that this specific gene only explains roughly 14 percent of the effect, and there are other genes spread over the other chromosomes. It's a very complex effect with many social influences.
Another well-known observation was that the younger brothers are increasingly likely to be gays. The "Freudian" theories meant to explain this effect psychosocially (punishing father, protecting mother) have been dead for quite some time. It was never found that psychosocial aspects of life and education had any effect on homosexuality whatsoever. Today, the experts clearly lean towards the explanation (of the homosexual younger brothers) based on "the hatred between the genders", more precisely on the defensive reaction of the maternal body against a male embryo.
The biologists have already found the gene responsible for the masculanization of the body - one that suppresses the development of female organs. Also, the scientists have isolated three active candidate genes on the Y chromosome responsible for the masculinization of the brain.
When these genes appear in the body of the mother, an immunity reaction is initiated, and this reactions gets stronger with every new "male" pregnancy. The mother's body is fighting against the "alien" and the changes of the hormonal adjustment of her organism may influence the development of the embryo's brain.
The anatomy of "straight" and "gay" male brains differ. Issues such as sexual orientation are therefore "programmed" not only when the new life is created, but also when the embryo is developing. The unknown "black hole" remains the period of several months after the birth, and not much is known what is happening with the new baby in this period.
The Italians only assign 7 percent to the hormonal influences in mother's body, which makes up 21 percent, and they argue that the remaining 79 percent remains a mystery. Note that if the explanation of these 79 percent were non-genetic in character at the end, one does not really face Darwin's paradox for these 79 percent.
Homosexuality is not a purely human effect. It's been described on 450 species. For example, bonobos are apes in Africa and most of them are bisexual. 75 percent of their sexual games leads to no reproduction.