Con to the question "Is Sexual Orientation Determined at Birth?"
"All of the aforementioned research studies from four different countries, each utilizing large, countrywide samples, reveal that homosexual behavior is not genetically determined. Rather, the data find that human sexuality is malleable, and environmental experiences and influences can and do shape its expression. Moreover, these findings are supported by decades of anthropological and sociological evidence that reveal that rates of homosexual behavior fluctuate - sometimes greatly - with changes in the social, cultural, and legal climate. The more an environment affirms or encourages same-sex sexuality - whether an urban center or a university campus - the more homosexuality there will be in that setting."
"Legalizing Same-Sex Marriage Will Increase Prevalence of Homosexuality: Research Provides Significant Evidence," drtraycehansen.com (accessed June 12, 2009)