In some respects, cities are bottom-up processes, but they are also top-down initiatives – and elites soon develop. Religion is older than the city, but the elites quickly build temples and turn themselves into priests. As they become more powerful the temples they build also have huge storehouses. What you see is that the man who has a surplus of material is the powerful man. This is because everyone is living hand-to-mouth, and if you have a bad harvest one year, well, you're stuffed.

My bright idea: Civilisation is still worth striving for