Leaking into a completely different thread, so I may as well take this somewhere. Some people think it's possible. :P
Do you think people can change this if they really want to? Because I actually can, even though I consider myself straight. I can easily point out a good looking guy or something, everyone can. Dunno what's stopping people. I can't imagine suddenly being off my significant other because they were a different gender, yet I still wouldn't go for a male. I think everyone can force themselves to be in love with someone of the same gender. S'all just a trend in society.
Actually, I think sexuality only exists because of... Dare I say religion? Plus other factors, I know thaaat.
If we bring the animal debate into it... yeah. They just have sex to simply mate. Pretty sure they've worked it out that they can't with the same sex. That's all I'm capable of typing this tired though. Have fun.