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.
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.