NY Mag Article on Biology of Sexual Orientation

Here's an interesting article in New York Magazine on the biology of homosexuality,

One of the riddles still vexing geneticists is why only 50 percent of gay identical twins share a sexual orientation with their sibling, despite being genetically identical. “We know from all sorts of research that it’s not your upbringing, not relationship with parents or siblings, not early-childhood sexual experiences and whether you go to a Catholic school or not,” says Sven Bocklandt, a geneticist at UCLA. “What I believe is that it is the ‘epigenetics environment,’ meaning the environment on top of our DNA—meaning the way that the gene is regulated. If you have identical twins, the genes are identical, but they are used differently. Every man and every woman has all the genes to make a vagina and womb and penis and testicles. In the same way, arguably, every man and woman has the genetic code for the brain networks that make you attracted to men and to women. You activate one or the other—and if you activate the wrong one, you’re gay.”

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Some critics of sexual-orientation researchers blame them for minimizing the role of experience in determining our affectional course in life. The feminist biologist Anne Fausto-Sterling has waged a constant battle against their research, which she calls “a big house of cards” that ignores the power of environment in creating personality. Nurture, she argues, can and should be studied as a link to sexual orientation. The baby penguin raised by her two dads is a potential case study—though genetically unrelated to either parent, in the last few mating seasons she has mated with another female.

The rush to declare a biological mandate is motivated by a political agenda, says Fausto-Sterling, the author of Sexing the Body, who is married to a woman after a marriage to a man. “For me and for any feminist, I think it’s a pretty fragile way to argue for human rights. I want to see the claims for gay rights made on moral, ethical, legal, and constitutional bases that don’t rely on a particular scientific view of sexual development.”

And according to the wikipedia entry on Biology and sexual orientation,

The Advocate, a U.S. gay and lesbian newsmagazine, reported in 1996 that 61% of its readers believed that "it would mostly help gay and lesbian rights if homosexuality were found to be biologically determined".[23] A cross-national study in the United States, the Philippines, and Sweden found that those who believed that "homosexuals are born that way" held significantly more positive attitudes toward homosexuality than those who believed that "homosexuals choose to be that way" and/or "learn to be that way".[24]

Also mentioned in the David France, New York Magazine article,

Sheep are among 500 animal species where homosexuality has been documented. They are also among the few who practice exclusive homosexuality, like many humans. In any population of sheep, about 8 percent of males show exclusive homosexual behavior. Little is known about the romantic life of Sapphic sheep because ewes tend to express their sexual interests by standing entirely still, yielding no clues about their partner preferences.