Genetics

Genetic and Environmental Influences on Individual Differences in Attitudes Toward Homosexuality: An Australian Twin Study

"The results suggest that variation in attitudes toward homosexuality is substantially inherited, and that social environmental influences are relatively minor."

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2292426/

Eight major studies of identical twins in Australia, the U.S., and Scandinavia during the last two decades all arrive at the same conclusion: gays were not born that way.

http://www.hollanddavis.com/?p=3647

http://www.youtube.com/watch?v=Gq9A40F_P10