The further upstream of that is large super structures of human social web cannot exist. There is no monoculture anymore and that has both pros and cons.
That's interesting and I hadn't really considered that for most of history, children grew up in a pretty un-diverse environment. You lived with your tribe and your extended family for the most part. In cities, ethnic and religious groups tended to self-segregate. The social rules were clear, and there was a lot less room for doubt about who you were and where you fit in.
