I'm reading Ambiguity and Sexuality: A Theory of Sexual Identity by William S. Wilkerson. In it, Wilkerson (a philosopher who identifies as gay) lays out his theory on how sexual identity - any sexual identity - is constructed.
And "constructed" is the key word, since he rejects the view of many gay rights activists that one is simply "born gay." He contends (and I agree with him) that such a position is merely a knee-jerk reaction to anti-gay criticisms of "choosing a sinful lifestyle" or what have you. This entire "choice vs. genetics" debate - like its close relative, the "nature vs. nurture" debate - is a false dichotomy which leads to both sides being wrong.
I'm only about a third of the way through the book (it's a slow read; he uses a lot of academic jargon and I haven't formally studied philosophy in three years), but a summary of his thesis - filtered through my own interpretation - goes something like this:
There probably is a genetic predisposition to homosexual or heterosexual desires. Some people's genes make them more likely to have one or the other. Then, almost immediately, you have the influence of prenatal conditions on the development of the brain, which can change whether and how these genes express themselves. After birth, children are right away conditioned with society's construction of gender: boys are given trucks and blue clothes, girls are given dolls and pink clothes, all before they can even speak. And, because gender and sexual orientation are almost inexorably tied together in our culture, children are taught that liking boys is "girly" and liking girls is "boyish."
Now, there's going to be a lot of variation in children's upbringing. Some parents/teachers/neighbors are going to be more open-minded about gender expression than others, so some will say it's perfectly okay for girls to play with army men or whatever, and some will refer the kid to a shrink. All these experiences are filtered through children's brains and interpreted based on the outcomes of previous experiences and that little thing called free will, which allows people to outright reject what society tells them.
So it basically goes like this: desire -> interpretation of desire -> acting (or not) upon desire based on interpretation -> societal reaction -> interpretation of societal reaction -> adjustment to sexual paradigm -> interpretation of next desire based on new paradigm -> and the cycle continues again and again and again throughout the course of a person's life. There is no beginning or end to this circle; even before the first desire came about, people still had a rudimentary sexual paradigm based on what they see around them, which was in turn colored by their internal thoughts and feelings. Eventually, people build up mental maps that they use to interpret their sexual desires and actions, and depending on how they've constructed their maps they may adopt many different identities based on similar personal histories.
Take me, for example. I didn't have any conscious attraction to other women until high school. I'd had one boyfriend previously, but I never really cared for him; I just was in a relationship because it seemed like a desireable thing. Now, given these facts, I could have determined that I really didn't like men at all - that I had just been told by society to be heterosexual, when in "reality" I was solely attracted to women. My feelings for women at the time certainly seemed much more real and intense than anything I'd ever felt for guys.
Conversely, because of my budding feminist consciousness at the time, I could have concluded that my attractions to women were the result of internalizing the male gaze - that is, I was so used to seeing women portrayed through the lens of heterosexual male experience (i.e. as objects of desire), I basically was trained to desire them myself. I certainly remember thinking about how women were just inherently prettier than men, and so much nicer to look at/draw.* Therefore, my same-sex attractions weren't "real" - they were a result of patriarchal conditioning.
However, I chose neither of these options. I chose to accept my same-sex desires as "genuine", while acknowledging my history of being attracted to men. Therefore, I concluded, I am bisexual. The thing is, though, I did not make the "right" decision. NONE of these possibilities I've just outlined are "wrong" or "right." They're just different decisions, and it wouldn't have really mattered which one I chose. I'm incredibly happy with where I am right now in my sexuality, but choosing another identity for myself would have set me on a completely different trajectory, and I probably would have been just as happy there, too.
I suppose the point I'm trying to make is that, yes, sexual identity is constructed - both consciously and unconsciously - out of our desires and experiences and interpretations, but just means that no one form of sexuality is more "valid" than another. If a woman's been in a heterosexual marriage for fourty years, then decides to divorce and adopt a lesbian identity, she's no "less" of a lesbian than a woman who's been solely attracted to other women as long as she can remember. The only thing that matters is how one personally interprets and understands one's sexual identity - and that others respect one's sexual identity.
*Now I think that's just silly. Both men and women are beautiful - just for different reasons. And it really makes me sad that men aren't used as artistic nudes, etc, more often.