That proves nothing, especially that it's "natural".
How does it not? Animals react on instinct...not on 'choices'. How can it's occurance in nature be anything but natural?
Are you sure you want to use the animals do it argument? Before you rest anything on this argument consider other things animals do on instict.
Incest
beatiality
Some animals kill thier mate durring or after sex
Some animals eat thier new born children
many animals willl kill compitition for a mate.
These sadly occur sometimes with us humans. Not sure about bestiality but the rest are instinctive for some species. And we humans do still have instincts. Fight or flight for example. It wouldn't be a big leap that male/female attraction was part of our makeup.
