Early Chinese civilization began around 2070 BC in the Huang He (Yellow River) valley, with important dynasties including the Xia, Shang, and Zhou dynasties. Government was organized under a series of dynastic rulers, with kings serving as both political and religious leaders assisted by priests. The economy was based around agriculture, with rice grown in southern China and wheat in northern China, in addition to trade and mining. Religion involved worship of nature deities and ancestors, with kings performing sacrifices. Writing began as early as 1500 BC using oracle bones, and architecture featured symmetrical designs with column support.