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 specific cultural regions that developed Chinese civilization were the Yellow River civilization, the Yangtze civilization, and Liao 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.