You have just as much access to the evidence as I do.
Originally Posted by Columcille
From there, also see the evidence for Environmental (nurture) and Biology (nature).
There is no consensus among scientists about the exact reasons that an individual develops a heterosexual, bisexual, gay, or lesbian orientation. The main reasons cited include genetic and environmental factors, likely in combination.
The American Academy of Pediatrics has stated that "sexual orientation probably is not determined by any one factor but by a combination of genetic, hormonal, and environmental influences".
The American Psychological Association has stated that "there are probably many reasons for a person's sexual orientation and the reasons may be different for different people". It stated that, for most people, sexual orientation is determined at an early age.
The American Psychiatric Association has stated that, "to date there are no replicated scientific studies supporting any specific biological etiology for homosexuality. Similarly, no specific psychosocial or family dynamic cause for homosexuality has been identified, including histories of childhood sexual abuse".