Homosexuality Not Chosen Says Expert

From San Francisco:

The final witness for gays and lesbians seeking to overturn California's ban on same-sex marriage testified Friday that most people don't choose their sexual orientation, few people change it and "conversion therapy" is useless and potentially harmful.

"The vast majority of people are consistent in their (sexual) behavior, their identity and their attractions," Gregory Herek, a UC Davis psychology professor, said at the San Francisco federal court trial on the constitutionality of Proposition 8.

I'm at a loss to understand. My familiarity with the roots of human behavior details two categories, 1) that which is learned (environmentally-derived), and 2) that which is hereditary (genetic).

Therefore, according to my likely-flawed understanding, the only way for gays and lesbians to not choose their lifestyle would be for it to be genetically pre-programmed. So far, my reading hasn't found any research which identifies the "gay and lesbian" gene.

Based upon my non-professional glance at the subject, Professor Herek's contention that people don't choose their sexual orientation must be wrong. Either that or Mr. Herek is not only a psychology professor but also a cutting-edge hobbyist in research genetics who hasn't reported his latest ground-breaking findings.