Physician and Founder of the Institute for Sexual Sciences
Pro to the question "Is Sexual Orientation Determined at Birth?"
"In the embryonic state, people are bisexual, but in the course of their natural development, most lose their desire for members of the same sex. These people are the heterosexuals, who love members of the opposite sex. Another category consists of those individuals whose sexual organs develop normally but in whom the desire for same-sex individuals in the feeling center fails to recede. The results are men who love men and women who love women."