““This precocious advance may have had a lot to do with the nature of the plain between the Yangtze and Yellow rivers. The territory is well suited both for agriculture, which leads to population growth, and for warfare, the two principal propellants of state formation. A relentless process of consolidation forced tribal systems to yield to states. In 2000 BC, a large number of political entities—traditionally put at 10,000—existed in the Yellow River valley. By the time of the Shang dynasty in 1500 BC, these had dwindled to some 3,000 tribal chiefdoms. The Eastern Zhou dynasty began in 771 BC with 1,800 chiefdoms and ended with 14 entities that were much closer to states. During the ensuing Warring States period, which lasted from around 475 BC to 221 BC, the 7 remaining states were reduced to 1. China””
