I'd like to give some more research for anyone who'd like to learn more.
BYU Professor Bill Bradshaw on a Biological Origin of Homosexuality" (ref. http://mormonstories.org/?p=1158)
animals displaying homosexual behavior: http://en.wikipedia.org/wiki/List_of_animals_displaying_homosexual_behavior
hemaphrodite (male/female) creatures: http://en.wikipedia.org/wiki/Hermaphrodite
hemaphrodite Leopard slugs engaging in 'perverse' sex: http://www.youtube.com/watch?v=FhVi4Z6CjZk
What prompted my response was a comment made by the second highest leader in the LDS church who said that god would not make a person gay. What is interesting is that he has made animals gay, animals and humans hemaphrodites, and many other things.
Is there just one cause of sexuality, either straight or gay? I don't know, but if we question how a person is gay, we must also have to question how a person is straight.