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 writing
It is generally agreed that true writing of language (not only numbers, which goes back much further) was independently conceived and developed in at least two ancient civilizations and possibly more. The two places where it is most certain that the concept of writing was both conceived and developed independently are in ancient Sumer (in Mesopotamia), between 3400 and 3300 BC, and much later in Mesoamerica (by 300 BC) because no precursors have been found to either of these in their respective regions. Several Mesoamerican scripts are known, the oldest being from the Olmec or Zapotec of Mexico.