The more this metaphor is fleshed out the more it sounds like it's referring to civilization in general and how ancient cities/city-states actually operated (to some level of similarity).
Build a city, invite people in, tax them and rule them, and destroy or absorb every rival you can get away with. Have technology or resources your competitor doesn't have? Sucks to be them.
I guess I'm not that surprised that even though we can collectively build better systems for ourselves after time and lots of understanding where the alternatives lead us, our nature shows itself in various other areas.