In Western societies where the nuclear family became "the norm" in the last century, lifelong marriage was THE LAW, and people who divorced were social outcasts, unless they were very wealthy (laws and customs for the masses have never applied to the very wealthy). That is why so many of us are wandering around with the cultural assumption that one single lifelong monogamous relationship is the "best" for everyone, even though nowadays it is pretty rare.

And why is it the men presume that a polyamorous relationship for them would mean "two wives"? It could just as easily mean that they would share a wife/partner with another man. I'm beginning to wonder how much some of you who claim to know about this subject, actually know? I suggest folks read here, for starters:

http://www.lovemore.com/