In the pre-historic world...we don't have a very good picture of what romantic partnership looked like. There is at least significant evidence of non-monogamous multi-male and multi-femal sexuality...with the insanely high levels of human sperm competition being among the most significant in my mind. But the details are non-obvious.
In the historic, agricultural world, we have a pretty good picture of what romantic partnership looked like. Man works 90 hour week to grow food to feed family. Woman works 90 hour week to clean house, cook food. Kids work 30 hour weeks to help...or else GTFO of the way, and play until they're grown enough to help. Childrearing past 2 isn't even a topic, because no one has time for it, and the kids raise themselves. The economics of the arrangement + the economics of childbirth work together to make females subservient.
Between 1900 and 1970, the world changed dramatically. The number of hours required to feed the family shifted from 90 down to near 10 (Still dropping). The number of hours *required* (fast food, appliances, TV dinners, etc.) to clean/cook/etc. dropped from 90 down to near 10. And the economics of chastity are destroyed by the Birth Control Pill. So the weekly total number of labor hours that used to be needed by a family used to be around 180 (there are 168 hours in a week)...and now it's near 20. Children have historically raised themselves, with very minor input from the adults...and now they go to school, which is equivalent to no (parental) adult input.
What is the modern (dyadic) function of the agricultural institution of marriage? At the higher end of the socioeconomic spectrum...the addition of a high-end male makes a huge difference to the income stream. At the lower end? Current incentives may well make the addition of a male to a single-woman's life economically negative.
The economics and game theory are going to win over time...regardless what anyone wants to happen. The question is what result does the game theory want (ooh, look, personification *and* telelology)?