> "Mother Nature is against monogamy!"

That's a fact.

97% of mammal species, and 100% of social apes, are NOT monogamous.

Looking at mammals, at least (and we are such), it looks like Mother Nature really dislikes monogamy.

To be more precise, though, what Mother Nature really favors is evolutionary success. Thus the mating strategy that better suits the species’ reproductive success. For most mammals it seems promiscuity, while for most birds it’s monogamy. It really depends.