Ehhhh no, I mean, the modern conception of monogamy is increasingly euro-centric around the world, but it totally existed independently in most places, even in historically matrilineal cultures. But sometimes certain small ethnic groups would have elements of polyandry or polygyny adapted to local conditions. These are what’s being lost to history.

Modern polyamory is in the lineage of a very middle class liberal (and at times utopian socialist) reaction to cultural alienation that can be traced back to the Free Love movement of the 18th and 19th centuries. Elements of this movement made their way into Anarchist circles in the 1890s and have stuck around in the western left ever since.

Pretty much, at least the modern nuclear family is religious-patriarchal propaganda. For most of human history, IE pre agricultural revolution, nearly all hunter-gatherer tribes weren’t monogamous… I think the average adult had an estimated 4 ongoing sexual relationships at one time, from what we can tell from still existing hunter-gatherer tribes.

Also none of our close primate ancestors are monogamous. There are a tiny number of monogamous primates, but they’re extremely far from us in lineage, IE tree monkeys with long tails that have sex once a year.

Our closest primate relations, are bonobos and chimpanzees, both of which have sexual habits pretty much the opposite of what religious and patriarchal propaganda tells us how humans “should” live.

A really good book about this is “Sex at Dawn”, which is a really great dissection of pre-class-society human sexual behavior.