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.
Cradle of civilization
Drawing on archaeology, geology and anthropology, modern scholars do not see the origins of the Chinese civilization or history as a linear story but rather the history of the interactions of different and distinct cultures and ethnic groups that influenced each other's development. The two specific cultural regions that developed Chinese civilization was the Yellow River civilization and the Yangtze civilization. Early evidence for Chinese millet agriculture is dated to around 7000 BC, with the earliest evidence of cultivated rice found at Chengtoushan near the Yangtze River, dated to 6500 BC. Chengtoushan may also be the site of the first walled city in China. By the beginning of the Neolithic Revolution, the Yellow River valley began to establish itself as a center of the Peiligang culture which flourished from 7000 to 5000 BC, with evidence of agriculture, constructed buildings, pottery, and burial of the dead. With agriculture came increased population, the ability to store and redistribute crops, and the potential to support specialist craftsmen and administrators. Its most prominent site is Jiahu. Some scholars have suggested that the Jiahu symbols (6600 BC) are the earliest form of proto-writing in China. However, it is likely that they should not be understood as writing itself, but as features of a lengthy period of sign-use which led eventually to a fully-fledged system of writing. Archaeologists believe that the Peiligang culture was egalitarian, with little political organization. It would eventually evolve into the Yangshao culture (5000 to 3000 BC), and their stone tools were polished and highly specialized. They may also have practiced an early form of silkworm cultivation. The main food of the Yangshao people was millet, with some sites using foxtail millet and others broom-corn millet, though some evidence of rice has been found. The exact nature of Yangshao agriculture, small-scale slash-and-burn cultivation versus intensive agriculture in permanent fields, is currently a matter of debate. Once the soil was exhausted, residents picked up their belongings, moved to new lands, and constructed new villages. However, Middle Yangshao settlements such as Jiangzhi contain raised-floor buildings that may have been used for the storage of surplus grains. Grinding stones for making flour were also found. Later, Yangshao culture was superseded by the Longshan culture, which was also centered on the Yellow River from about 3000 to 1900 BC, its most prominent site being Taosi. The population expanded dramatically during the 3rd millennium BC, with many settlements having rammed earth walls. It decreased in most areas around 2000 BC until the central area evolved into the Bronze Age Erlitou culture. The earliest bronze artifacts have been found in the Majiayao culture site (3100 to 2700 BC).