Mesopotamia was part of the Fertile Crescent, where settled agriculture first developed (see “The Development of Horticulture” in Chapter 1). The earliest agricultural villages in Mesopotamia were in the northern, hilly parts of the river valleys, where there is abundant rainfall for crops. Farmers had brought techniques of crop raising southward by about 5000 B.C.E., to the southern part of Mesopotamia known as Sumer (soo-MAIR). In this arid climate farmers developed large-scale irrigation, which required organized group effort but allowed the population to grow. By about 3800 B.C.E. one of these agricultural villages, Uruk (OO-rook), had expanded significantly, becoming what many historians view as the world’s first city. Over the next thousand years, other cities emerged in Sumer. These cities built defensive walls, marketplaces, and large public buildings; each came to dominate the surrounding countryside, becoming city-states independent from one another, though not very far apart.

The city-states of Sumer relied on irrigation systems that required cooperation and at least some level of social and political cohesion. The authority to run this system was, it seems, initially assumed by Sumerian priests. Encouraged and directed by their religious leaders, people built temples on tall platforms in the center of their cities. Temples grew into elaborate complexes of buildings with storage space for grain and other products and housing for animals. Surrounding the temple and other large buildings were the houses of ordinary citizens, each constructed around a central courtyard.

To Sumerians, and to later peoples in Mesopotamia as well, many different gods and goddesses controlled the world, a religious idea later scholars called polytheism. Each deity represented cosmic forces such as the sun, moon, water, and storms. The gods judged good and evil and would punish humans who lied or cheated. People believed that humans had been created to serve the gods and generally anticipated being well treated by the gods if they served them well.