I agree that the purpose of mating behavior is reproduction. You are over simplifying the concept of marriage. There are other economic and societal factors involved which cannot be explained by your over-simplification. We do not live in primitive times anymore where survival instincts dominate our way of living.<quoted text>
Not subjective at all.
The whole purpose of mating behavior is reproduction. A drive that is at least equated to our desire for air or water.
A duplicate gendered couple is absolutely incapable of fulfilling mating behavior. Pointless.
Here is a question for you;
Why does a butch lesbian dress and act like a man to attract another lesbian?
Animals also exhibit homosexual behavior for survival reasons: to limit overgrowth in population. This behavior increases the longevity of the herd as more resources will not be required for the herd. Some birds have 2 male and 1 female to raise their offspring as this ensures their survival. Again, these acts serve a purpose. It may not be to reproduce, but, evolutionarily, to ensure the survival of their offspring. Not pointless.
Why a butch lesbian looks like a man...I never really thought about it. Why?