At best,
the evidence for a genetic and/or biological basis to homosexual orientation is inconclusive. In fact, since the early 1990s, numerous studies attempting to establish a genetic cause for homosexuality have not proven to be valid or repeatable – two important requirements for study results to become accepted as fact in the scientific community.
Because of this, the current thinking in the scientific community is that homosexuality is likely caused by a complex interaction of psychosocial, environmental and possible biological factors. And the two leading national psychiatric and psychological professional groups agree that, so far, there are no conclusive studies supporting any specific biological or genetic cause for homosexuality.
In sum, there is no scientific or DNA test to tell us if a person is homosexual, bisexual or even heterosexual for that matter. And since nobody is "born gay," it's clear that sexual orientation is, at its core, a matter of how one defines oneself – not a matter of biology or genes.
Clearly, the case for a "gay gene" has not been made.
So, do all gay people believe that sexual orientation is "fixed" and unchangeable?
Not by a long shot. While it's true that many homosexuals and their allies believe that people are "born gay" and cannot change, there exists a surprising – and not insignificant – minority of gays and lesbians who recognize that sexual orientation is, in fact, flexible.
We are sexual beings, yet this does not mean that we are born homosexual, bisexual, or heterosexual. Our sexual expression can change over time, towards different people, through different experiences. A lack of understanding about this type of human variability often leads to a perspective that our genes define who we are. Each of the above areas of research displays findings that hinge on the assumption that a given individual’s sexual expression neatly fits into the categories “straight” and “gay.” By not considering evidence of human sexual fluidity, debates regarding origins and biology are not substantial or complete. Current efforts fail to tell the whole story. And even if we were to accept that the assigned sexual orientation of the individuals participating in these studies accurately reflected their lifelong expression, conclusive proof of a link between this and their genes has yet to be found.