Cities concentrated people and power, and they required more elaborate mechanisms to make them work than had small agricultural villages and foraging groups. These mechanisms were part of what political scientists call “the state,” an organization in which a small share of the population is able to coerce resources out of everyone else in order to gain and then maintain power. In a state, the interest that gains power might be one particular family, a set of religious leaders, or even a charismatic or talented individual able to handle the problems of dense urban communities.

However they are established, states coerce people through violence, or the threat of violence, and develop permanent armies for this purpose. Using armed force every time they need food or other resources is not very efficient, however, so states also establish bureaucracies and systems of taxation. States also need to keep track of people and goods, so they sometimes develop systems of recording information and accounting. These systems allow for the creation of more elaborate rules of behavior, often written down in the form of law codes, which facilitate further growth in state power, or in the form of religious traditions, which specify what sort of behavior is pleasing to the gods or other supernatural forces.

Written laws and traditions generally create more elaborate social hierarchies, in which divisions between elite groups and common people are established more firmly. They also generally heighten gender hierarchies. Those who gain power in states are most often men, so they tend to establish laws and norms that favor males in marriage, property rights, and other areas.

Whether we choose to call the process “the birth of civilization” or “the growth of the state,” in the fourth millennium B.C.E., Neolithic agricultural villages expanded into cities that depended largely on food produced by the surrounding countryside while people living in cities carried out other tasks. The organization of a more complex division of labor was undertaken by an elite group, which enforced its will through laws, taxes, and bureaucracies backed up by armed force or the threat of it. Social and gender hierarchies became more complex and rigid. All this happened first in Mesopotamia, then in Egypt, and then in India and China.