History of the world
Whether in prehistoric or historic times, people always needed to be near reliable sources of potable water. Settlements developed on river banks as early as 3000 BCE in Mesopotamia, on the banks of Egypt's Nile River, in the Indus River valley, and along China's rivers. As farming developed, grain agriculture became more sophisticated and prompted a division of labour to store food between growing seasons. Labour divisions led to the rise of a leisured upper class and the development of cities, which provided the foundation for civilization. The growing complexity of human societies necessitated systems of accounting and writing.
History of Mesopotamia
The Fertile Crescent was inhabited by several distinct, flourishing cultures between the end of the last ice age (c. 10,000 BC) and the beginning of history. One of the oldest known Neolithic sites in Mesopotamia is Jarmo, settled around 7000 BC and broadly contemporary with Jericho (in the Levant) and Çatal Hüyük (in Anatolia). It as well as other early Neolithic sites, such as Samarra and Tell Halaf were in northern Mesopotamia; later settlements in southern Mesopotamia required complicated irrigation methods. The first of these was Eridu, settled during the Ubaid period culture by farmers who brought with them the Samarran culture from the north. This was followed by Uruk period and the emergence of the Sumerians.