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 the Americas
The Olmec civilization was the first Mesoamerican civilization, beginning around 1600-1400 BC and ending around 400 BC. Mesoamerica is considered one of the six sites around the globe in which civilization developed independently and indigenously. This civilization is considered the mother culture of the Mesoamerican civilizations. The Mesoamerican calendar, numeral system, writing, and much of the Mesoamerican pantheon seem to have begun with the Olmec.