I find this sexist. To somehow frame it as science that women need to marry up because they are designed to do so... where are you getting this?

For starters, to state that it is a woman's core nature to "marry up" is using this term rather loosely. Hypergamy is a social science, meaning it is rooted in social constructs, social constructs that are primarily patriarchal. Historically, it is for sheer survival that women had to better their circumstances. Marriage was means. Women were not designed to depend on men, they had to depend on men based on social constructs.

Today women have more choices. Woman can choose to find a husband who makes more money, just like husbands can find a wife who makes more money as well. And sometimes choices are not so clear cut, especially for individuals with MI who might be unable to work (whether this is permanent or temporary) and have no family or means to support themselves.

That said, women still make less than men in many industries, and if a couple wants to start a family, then we have to remember that while maternity leave is effective, it also leaves women out of work with less of an opportunity to hone or keep their skills fresh.

And, at the end of the day, none of this means the relationship would be fulfilling on an emotionally satisfying level.