Once they had invented the basic concept of irrigation, farmers dug canals to carry water over greater distances. But the construction and use of irrigation canals required planning and coordination. If farmers with fields near the head of the canal used too much water, those farther downstream could not irrigate their crops. Moreover, because flooding was a serious threat in the extremely flat Mesopotamian countryside, the canals and fields needed to be lined with strong dikes, which required maintenance. Such tasks demanded organization and cooperation in villages, as well as a system to resolve conflicts over water rights. From the very beginning, irrigation farming stimulated development of new forms of social organization and new connections among members of ancient communities.
Cooperation brought substantial benefits. In southern Mesopotamia, irrigation farmers could reap enormous yields and earn much more income than farmers elsewhere who relied on rainfall. Moreover, despite the absence of useful stone, trees, and metal, the region had several other rich natural resources. Near the rivers and canals, date orchards flourished, and they provided shade for vegetable gardens. In the rivers and marshes at the head of the Persian Gulf, inhabitants could catch loads of fish, as well as turtles, crabs, and water rats, which also provided protein. Herdsmen guided large flocks of sheep and goats to seasonal pastures. These diverse resources fueled the growth of larger communities and attracted outsiders, and the population of southern Mesopotamia rapidly increased after 5000 B. c.e.
The earliest settlers of Mesopotamia established villages like those of the surrounding Neolithic societies (see Chapter 1). All family members worked at agricultural tasks, some focusing on herding animals and others on growing crops. Because they cared for children, women were more tied to the house than men and had duties such as cooking and grinding grain. They made the pottery that modern archaeologists find so useful, and they wove sheep wool and goat’s hair into clothing, blankets, and other textiles.
To maintain a close relationship with their ancestors, people buried the dead beneath the house floors and gave them food and drink offerings. They even dug pipes into the floors of houses to pour these offerings into the tombs. They also provided grave goods— items buried with the dead. These goods provide evidence of social change in the villages during the centuries from 5000 b. c.e. to the time of the origin of cities, 3200 b. c.e. Certain tombs came to include more and richer goods, indicating that their owners had a special status in life. Scholars speculate that communities gave these distinctive goods to village leaders who settled disputes and coordinated labor. Thus, even at this early stage, we see evidence of the social hierarchy that would come to characterize Mesopotamian cities.
Another important development occurred during the same period. As we have seen, in early agricultural communities families performed all the tasks needed to grow crops, raise livestock, and gather additional food. Over time, however, specialization of labor developed, which made production more efficient. Specialist farmers, gardeners, herdsmen, and fishermen produced higher yields than families who undertook these tasks on their own. Specialization of labor also led to technological innovation. For example, Mesopotamian farmers invented a plow that dropped seeds into the furrows as it cut open the earth, speeding up the work of planting and ensuring that seed was used efficiently. As labor became more specialized, a new necessity arose: families that were formerly self-sufficient had to trade to meet some of their basic needs. This crucial need for exchange was a major stimulus to the development of cities. People needed a central place to meet, a crossroads where they could connect with potential trading partners and exchange goods.
Many of the world’s early urban cultures grew up in the valleys of mighty rivers, most notably in Mesopotamia along the Tigris and Euphrates, in Egypt along the Nile, in South Asia along the Indus, and in China along the Yellow (Huang He) and Yangzi rivers. With this in mind, many historians make a connection between irrigation agriculture and the centralized authority and social hierarchy typical of many ancient urban cultures. This line of argument suggests that irrigation depends on a strong central authority to coordinate its construction, use, and maintenance. Archaeological research does not, however, support this argument. Rather, the evidence shows that small communities initiated and maintained irrigation projects; centralized authority developed only long after such projects had begun. Nonetheless, it was the rich agricultural potential of the river valleys that led people in many parts of the world to establish densely populated urban centers.