I think that's a pretty broad oversimplification which is, for the most part, disproven by the fact that gays and lesbians often choose to have monogamous relationships.Bara_no_Hime said:Ah! See, this suddenly makes sense to me. Reproductive jealousy - you are upset by the idea of sharing or poly because it would make you question the paternity of your potential children.
The real reason, I believe, is simply because monogamy is a societal norm in the Western world these days. There's no real "logic" to it, it's just how our culture has evolved.
I wouldn't be closed to the idea, but I can't really imagine the circumstances that lead up to such an arrangement. If you're satisfied with your relationship the way it is, why involve a third person? And if you're not, then surely there are deeper issues involved that won't be resolved merely by bringing another person into the mix as a distraction.