[Symmetry]

There was a tremendous amount of social technology that had to be developed to allow people to regularly interact with strangers without trying to kill each other.

EDIT: Which is to say, a global community of 7 billion is absurd but not all that much more absurd than a city-state of 50 thousand.

[hyperpallium]

There's an intriguing but hard to prove theory that some popular religions (Christianity, Buddhism) arose as cities became more populous, and in response to that. Part of your "social technology".

Perhaps we'll soon see a new religion?

[axplusb]

On that topic Harari's Homo Deus is a pretty interesting read. He argues that Humanism is the de facto "new" (2-3 centuries old) religion. Soon to be replace by the celebration of something even more global -- data.

[stult]

Our Data, Who art in the Cloud, hallowed be Thy Index, Thy Algocracy come, Thy Classification be done, in IoT as it is in the Cloud, lead us not into Underfitting, but deliver us from Anecdotal Reasoning. For Thine is the algocracy and the market share and the celebrity: of the Network, and of the Server, and of the Holy Algorithm, DateTime.Now() and ever, and unto ages of ages. Amen.

[Symmetry]

Maybe, I have Big Gods: How Religion Transformed Cooperation and Conflict on my reading list but that seems to be more a part of later developments than city states. Before that came written laws, and before that came having states. I guess I'd recommend reading The World Until Yesterday followed by The Origins of Political Order.

[solatic]

https://www.theguardian.com/news/2017/jul/11/how-economics-b...

[vivekd]

but we know that's not true. In the case of Christianity it arose in rural areas and was opposed by urban governments. Also, it did not spread in conjunction with urbanization but instead spread suddenly.