Only 1 species was given knowledge of God. Homosexuality may well be natural for animals, but contrary to Darwinian thought (which, scientifically, is obsolete), man is not an animal. We share characteristics in common with animals, but we are not animals. Animals have no conscience and are incapable of making moral and ethical decisions. They can act only on instinct. Man alone is able to reason and consider the consequences of actions and then make a decision on what course of action to take. You might teach a dog not to do something, and he might get a guilty look when caught doing it, but it is not a moral/ethical guilt, but rather the expectation of punishment he's trained to know is to come. And it was only to man that God said homosexuality is a sin. It doesn't matter how you try to rationalize it, it's a sin today, it was a sin yesterday, and it's still going to be a sin tomorrow. So are a lot of other things. Sin is not what man was created for, and we are expected to rise above sin with God's help.