There is a difference between what is created by nature or instinct and what is a social construct aka environmental.
The very first evolutionary forms of every animal were not choosing not to breed.
If that were the case then nothing would have evolved would it? The fact that
some animals don't breed
today is a reaction to the environment and the social structure that they developed over time.
Exceptions aside, the rule of nature has been stated again and again and you are choosing to ignore it. That makes you ignorant.
And if you needed reassurance of your ignorance:
I already answered your question in my third post in this awful, awful thread.
http://www.lpsg.org/138901-some-say-gay-unnatural-2.html#post2194916
All (heterosexual) animals WANT to reproduce. In cases where an animal fails to reproduce, social roles take priority over their own instinct to procreate.
eg they are a submissive member of the pack or social group
eg they are a 'worker' and not a viable breeding partner
In fact, 90% of males in the animal kingdom die as virgins. They are nature's failures.
Yes it is cruel but it is also
TRUE.