I notice that some anthropologist believe all humans were egalitarian in the past, and others believe inequality was more common they we currently we think with hunter gathers.
This seems to along with anthropologist using modern hunter gathers as way to look at the past which is now considered not a best practice from what I read. Which this influenced the egalitarian hunter gathers idea even more.
I'm gonna go against the grain and say that there even though economic structures varied wildly among prehistoric humans based on their material conditions, one aspect of human society that was common enough that you could call it the "default" is clans. We tend to stick with the people we're related to, periodically swapping members with other clans and budding off groups to form new ones, and this pattern happens to some extent no matter which pre-agricultural economic lifestyle you're living in.
But even norms of familial relationships, marriage practices, and the way that groups separate and join varies enormously. Some cultures don't have a recognized social role of a father, some determine who aunts and uncles and cousins are in very different ways than Western societies do, and so forth and so on.