In short, I don't know.
Did you really expect me to go do the scientific method in a blog post? You criticism is disingenuous. None of the 85% of cultures that preferred polygamy were competitive economically with the dominant Western monogamous cultures over the past couple of centuries.
Nature is adapting too fast to even apply the scientific method, i.e. there appear to not be repeatable instances, but rather a continual evolution. Although perhaps we might find a cycle if we could compile enough historical data.
So just accept that is for the most part won't be a concrete science.
It could. It might. It is possible.
Perhaps you prefer posit the theory (which you've alluded to) that engineers are just simpletons and want to enclose everything into a neat equation.
(I would guess it is both your theory and my theory combined. I know from my own personal experience and other engineers I've known that we do indeed prefer production over endless theoretical bullshit. I do like theory and philosophy, but I like it to end up somewhere within reasonable time frame; whereas, some academics make a career out of theoretical research that never produces any practical real world application/production.)
And perhaps I think your cohorts rather bloviate about various speculative causal interpretations from complex data sets (making arguments about evidence leaning towards), which from another perspective appear to be aliasing error and thus hogwash.
So we shouldn't blog because neither of us have any solid veracity. Blogging is often about expressing ideas and opinions.
Frankly, I almost didn't write this blog, because I did realize that the social sciences are far to complex and muddled to make absolute arguments. But I decided to proceed, because I sense there is a decadence associated with the new fondled idea of polygamy for Western culture. We are importing the barbarians again, repeating the fall of Rome.