We will refer to Ancient China as the time between the Neolithic period (ca. 6,000‒ ca. 1750 BCE) and the Han dynasty (206 BCE‒ 220 CE), which is roughly equivalent to the period of the Roman Empire in the West. This is the formative stage of Chinese civilization. During this time, what we now call China developed from a collection of isolated cultural communities to a set of organized states which eventually coalesced around the idea of a single unified state, and then expanded to include contact with other civilizations.