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.
Olmecs
The Olmec may have been the first civilization in the Western Hemisphere to develop a writing system. Symbols found in 2002 and 2006 date from 650 BCE and 900 BCE respectively, preceding the oldest Zapotec writing found so far, which dates from about 500 BCE.