What is natural?

There is much and constant debate over gay marriage, and why it is wrong or right. However, the main topic usually brought up is if it is something that is natural or unnatural. Biologically speaking there are reasons for why it may be unnatural to have a partner of the same sex, the main one being that there is no way to reproduce offspring. Research also shows that opposite sexes are mainly always attracted to each other. People also say that it is against human nature to want to be with the same sex, and as always the main factor being that it "offends god." Although people against gay marriage may have a few biological reasons to back up their argument and those reasons are important, they are blind to one main thing. Homosexuality is not only seen in humans all throughout history, but in all species. Rebutting the religious portion, If god would be so "offended" by homosexuality, he would not have created a world full of it. What is important is that all these species engaging in homosexual tendencies have been able to survive and thrive. Just because one has chosen a partner of the same sex, does not mean they are never going to reproduce offspring, especially today with modern medicine. The importance of this is to understand that homosexuality is natural and although not all my have these feelings (homosexuality), those who do are in no way acting unnatural, and deserve the same rights.