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 history
The Zapotec emerged around 1500 years BC. They left behind the great city Monte Alban. Their writing system had been thought to have influenced the Olmecs but, with recent evidence, the Olmec may have been the first civilization in the area to develop a true writing system independently. At the present time, there is some debate as to whether or not Olmec symbols, dated to 650 BC, are actually a form of writing preceding the oldest Zapotec writing dated to about 500 BC.