title: History of the world
context: 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,[3] on the banks of Egypt's Nile River,[4][5] in the Indus River valley,[6] and along China's rivers.[7][8]  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.
question: What is the earliest known civilization?
answers: 3000 BCE in Mesopotamia