http://www.ncbi.nlm.nih.gov/pubmed/18561014New evidence of genetic factors influencing sexual orientation in men: female fecundity increase in the maternal line.
There is a long-standing debate on the role of genetic factors influencing homosexuality because the presence of these factors contradicts the Darwinian prediction according to which natural selection should progressively eliminate the factors that reduce individual fecundity and fitness. Recently, however, Camperio Ciani, Corna, and Capiluppi (Proceedings of the Royal Society of London, Series B: Biological Sciences, 271, 2217-2221, 2004), comparing the family trees of homosexuals with heterosexuals, reported a significant increase in fecundity in the females related to the homosexual probands from the maternal line but not in those related from the paternal one. This suggested that genetic factors that are partly linked to the X-chromosome and that influence homosexual orientation in males are not selected against because they increase fecundity in female carriers, thus offering a solution to the Darwinian paradox and an explanation of why natural selection does not progressively eliminate homosexuals. Since then, new data have emerged suggesting not only an increase in maternal fecundity but also larger paternal family sizes for homosexuals. These results are partly conflicting and indicate the need for a replication on a wider sample with a larger geographic distribution. This study examined the family trees of 250 male probands, of which 152 were homosexuals. The results confirmed the study of Camperio Ciani et al. (2004). We observed a significant fecundity increase even in primiparous mothers, which was not evident in the previous study. No evidence of increased paternal fecundity was found; thus, our data confirmed a sexually antagonistic inheritance partly linked to the X-chromosome that promotes fecundity in females and a homosexual sexual orientation in males.
http://www.nature.com/nature/journal/v4 ... 5158b.htmlA population-genetic model indicates that if there is a gene responsible for homosexual behaviour it can readily spread in populations. The model also predicts widespread bisexuality in humans.
The first shows that it is evolutionary advantageous for a society to have homosexuals and the 2nd gives credence to the "gay gene" hypothesis. In light of these two things, can religions continue to accuse homosexuality of being unnatural and/or morally wrong? And how should this research affect the socio-political nature of the debate over equal rights?
