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 Maya civilization
The history of Maya civilization is divided into three principal periods: the Preclassic, Classic and Postclassic periods; these were preceded by the Archaic Period, which saw the first settled villages and early developments in agriculture. Modern scholars regard these periods as arbitrary divisions of chronology of the Maya civilization, rather than indicative of cultural evolution or decadence. Definitions of the start and end dates of period spans can vary by as much as a century, depending on the author. The Preclassic lasted from approximately 2000 BC to approximately 250 AD; this was followed by the Classic, from 250 AD to roughly 950 AD, then by the Postclassic, from 950 AD to the middle of the 16th century. Each period is further subdivided: