I would guess, having not studied the topic at all, that the tendency toward monogamy (or at least punctuated monogamy) long predates what you're talking about.

I would guess, having not studied the topic at all, that the tendency toward monogamy (or at least punctuated monogamy) long predates what you're talking about. It seems to me that people who are careful about insuring who they have children with will be much more successful at passing their genes on than people who are not so careful, and thus there ought to be some selective pressure for at least punctuated monogamy.