Changes

By the 4th and 3rd millennium BC, more complex societies developed with larger settlements. In particular in southern Mesopotamia (southern Iraq), where we see the first cities form. <ref> For information about 4th millennium BC canals and irrigation in southern Mesopotamia, see: Wilkinson, T. J. 2003. Archaeological Landscapes of the Near East. Tucson: University of Arizona Press, pg. 89.</ref> However, the region is very dry and depended heavily on two major rivers, the Tigris and Euphrates. Irrigation began to become more complex, with longer channels and managed by groups of people at different points, including controlling sluices that would release water to different areas. This development is similar to the Indus region along the Indian and Pakistani border, where the Indus river became important in dry regions as major cities developed. Similar types of canals to those of southern Mesopotamia seem to have developed, leading to also large cities by the 3rd millennium BC. <ref> For more information on irrigation in the Indus region, see: McIntosh, Jane. 2008. The Ancient Indus Valley: New Perspectives. ABC-CLIO’s Understanding Ancient Civilizations Series. Santa Barbara, Calif: ABC-CLIO, pg. 115 </ref>What is critical for these early systems is that they forced societies to better organize labor for construction and maintenance, which helped to encourage more complex organization and state formation. In essence, canals and irrigation likely had a major role in the development of some early, complex state societies developing in Mesopotamia and the Indus region.