Who decided that humans are a monogamous species, anyway? Because it is socially the "norm", obviously. but where did that come from - just the jealousy and insecurities that most people have? And with all the cheating going on in the world... maybe monogamy is just not meant to be?
Well, take out the nature aspect and you could probably narrow this down to religion. But I'm one of those people who think most organized religions are about control which is why I don't belong to one.