Barriers like oceans, mountains, and deserts isolated early China, but two major river systems, the Huang He and Yangtze, supported agriculture. The Huang He's floods could devastate villages but also left fertile silt. China's heartland in the North China Plain between the rivers became the center of civilization. The first dynasties like the Xia and Shang emerged around 2000 BCE, with the Shang establishing cities, writing, and social hierarchy. Under the Zhou dynasty starting in 1027 BCE, a system of feudalism developed where kings granted land to nobles in exchange for loyalty and service, though this contributed to instability and warfare between states over time.