The argument is also deeply flawed because "women can only have one man's baby at a time" ignores the fact that relationships last longer than a pregnancy. A woman could have two husbands and have kids with them sequentially, even in a world where the "having kids" part mattered.
It's not wrong. It's based in biology.
> Marriage has no requirement for reproduction.
In the same way that getting a law degree doesn't have a requirement of getting a job as a lawyer. But generally, you get a law degree to become a lawyer. The reason marriage was created was for family creation.
> The argument is also deeply flawed because "women can only have one man's baby at a time" ignores the fact that relationships last longer than a pregnancy.
What? How is that a flaw? Sure it last longer than the pregnancy because the kid is there.
> A woman could have two husbands and have kids with them sequentially
Right. And a man can have two wives and have kids with them in parallel.
> even in a world where the "having kids" part mattered.
Of course it matters. It's the basis of existence. It's a biological imperative of pretty much every human being.
I can't believe you are arguing against that.
People who can't or don't want to reproduce routinely get married. There is no legal requirement for reproduction, and people don't only get married for that reason.
You can't take the root causes for human behaviour and say they apply universally - e.g: humans want to eat more than they need to eat at that moment to stockpile a reserve - this behaviour is no longer relevant in most modern societies. Food is not about just fuelling our bodies today, even if that's the root of the behaviour "based in biology". Human desires and motives are distinct from the evolutionary reasons for them, and pretending they aren't is rejecting reality.
Your view is deeply and fundamentally flawed - it doesn't reflect reality as we see it in practice. Data models where you just throw away edge cases is failing to do the job well.
https://en.wikipedia.org/wiki/Polyandry
(specifically the part about partible paternity)
That's why polygamy has generally happened in only one direction throughout history.