To characterize the earliest societies we can draw on evidence from hunter-gatherers of recent centuries and the archaeological record. The vast countries that now cause hearts to swell with pride would have been unfathomable to our hunter-gatherer ancestors. We will explore what made this transformation possible, leading to societies that continue to discriminate against outsiders even though they have become so numerous that most members are unknown to each other. The casual anonymity that characterizes contemporary human societies may seem unremarkable, but it is a big deal. The seemingly trivial act of entering a café full of strangers without a care in the world is one of our species’ most underappreciated accomplishments, and it separates humankind from most other vertebrates with societies. The fact that the animals of those species must be able to recognize each individual in their society is a constraint most scientists have overlooked, but it explains why no lions or prairie dogs will ever erect cross-continental kingdoms. Being comfortable around unfamiliar members of our society gave humans advantages from the get-go and made nations possible.
From The Human Swarm: How Our Societies Arise, Thrive, and Fall by Mark W. Moffett