Historically speaking, slavery and civilization go hand in hand. Undermining the former might undermine the latter.

That's not to say that not having access to legal polygamous marriage and owning people are equal but to show that the argument doesn't really stand on it's own. The correlation between monogamy and civilization isn't necessarily causitative.

Also I'm not sure that monogamy is as paired up with civilization as you claim. Haven't Kings and leaders for large portions of history been known for their harems?

Do we actually know this for certain? We have a very curated view of many past civilizations and in many (most?) cases it is a very heteronormative view.

I have seen plenty of arguments that monogamy did not become "normal" until religion entered the picture and the idea of woman as property became a thing (ironically the fact that some religions reinforce this by a man having multiple wives).

There is absolutely no reason to believe monody and civilization matters in the slightest. At best you could argue (and I would agree) years ago needing to be concerned about a woman getting pregnant, but that does not hold any weight in a modern society.

That had more to do with "who owns what, and who gets what when they die" than anything else. (Citation needed...)

In a modern society with strong property rights and gender equality monogamy would be unnecessary from a purely "maintaining civilization as we know it" point of view.

...No comment on an emotional / psychological point of view.

Historically speaking, rich men having multiple partners so long as they could support them all (plus any resulting children) was the norm.

Maybe the real problem is we now think even rich men should tightly comply with expectations of monogamy when that was never the norm.

/Devil's advocate

Historically speaking horse was the only mean of transportation, hygiene was nonexistent, disease spread quickly and killed millions, warlords owned nearly everything for most of the recorded history, people used to believe in gods... (all these factors could contribute to monogamy)

That something was valuable and important in the history doesn't mean is it today. Do you seriously think our world is in any way similar to the world even just 100 years ago?

For a period of time, so did some form of monarchy. I believe this may be a correlation and causation issue.