This is not so much polyamory as it is polyandry, one female with several males. It is found in anthropology only in severely low resource areas, where it takes more than one male’s efforts to keep a woman and children alive. It only works if the males are very closely related, most typically brothers. That way, all the males are closely related to the child. Otherwise, conflicts among the males make the arrangement impossible.
Anyone with common sense knows this, and yet, there is a powerful public delusion that everyone can just screw anyone with no negative personal or societal outcomes.
Among the FR population, whose average age is quite high - I'm a youth at 53 - it is only men who proudly proclaim their promiscuity, but I understand there is more gender equality among young people.
And in those cultures inheritance was generally passed through the sister’s children. You KNEW at least half the dna was familial.
Even the idiots could figure out not to trust the groups.