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.
Ancient Near East
Sumer, located in southern Mesopotamia, is the earliest known civilization in the world. It lasted from the first settlement of Eridu in the Ubaid period (late 6th millennium BC) through the Uruk period (4th millennium BC) and the Dynastic periods (3rd millennium BC) until the rise of Assyria and Babylon in the late 3rd millennium BC and early 2nd millennium BC respectively. The Akkadian Empire, founded by Sargon the Great, lasted from the 24th to the 21st century BC, and was regarded by many as the world's first empire. The Akkadians eventually fragmented into Assyria and Babylonia.