No one really knows why some people are gay or lesbian and others are straight or bisexual. But what we do know is that homosexuality has existed all throughout history and is present in birds and mammals, as well as humans.
But is Being Gay a Choice?
Certainly those who believe homosexuality is a sin say it's a choice. Even some gay and lesbian people believe being gay is a choice. Most, however, believe that they were born gay or lesbian. The honest answer is, we think being gay is not a choice, but there hasn't been any conclusive studies to prove it.
What we do know is that therapies that attempt to change people from gay to straight have a very poor success rate. Sometimes people change their behavior, but the attraction is still there. My left-handed mother as a child was forced to use her right hand in school. She learned to change her behavior, but this did not change the fact that she is left-handed.
The thing you do have a choice about is your attitude about being gay, lesbian or bisexual. You can choose to hide your sexual orientation, or even be involved in a heterosexual relationship, but that does not mean you are not lesbian or bisexual.
What we do know is that people who are out and accepting of their sexual orientation live happier and more fulfilled lives than those who try to suppress their feelings or live their lives in the closet.