I really get tired of people who argue that the so called traditional nuclear family is "natural" because it takes both a man and a woman to make a baby. Indeed, so far it has required contributions of sperm from a man and an egg and womb facilities from a woman to make a baby. It does not follow, however, that any particular household form is superior when it comes to raising that baby. There's no logical connection between the statement of how babies get conceived, as matter of fact, and how babies should get raised, as a normative proposition. I have to go with the idea that there are any number of ways to raise babies without frakking them up, and that it isn't up to me to tell anyone else what their domestic arrangements should be.
As far as I'm concerned, what could be more unnatural than the so called traditional nuclear family? I doubt very much that our prehistoric forebears would have survived long in such an arrangement. On the contrary, they'd have banded together in larger extended family groupings.
To belabor the point, I reckon that matrilineal extended families with visiting spousal relations are as "natural" as anything else contrived by mankind. My nephews and nieces are as close to me genetically as my own grandchildren. Over the centuries, the difference will be negligible between my direct and indirect descendants in terms of relatedness. However, I'm just about 100% sure that my nieces and nephews are actually related to me and not changelings. My matrilineage will almost certainly be my kin whereas my patrilineage will be fraught with multiple risks of cuckoldry, and it takes only one of these to wipe out my genetic contribution.
It would be genetically stupid to adopt a patrilineal family structure unless we also adopt a costly and inconvenient social order that keeps women under strict control of their mates. What would be the point of such a regime, with all the misery and unhappiness that it would entail, when the matrilineal solution is available at much less cost and with much more personal freedom?
I'm not telling anyone how to live, mind you, but you could do worse than the matrilineal extended family.