There has been an uninterrupted history since 84 1. The records before 84 1 are intermittent or unclear, which can be pushed to about 2 100 BC, that is, early summer. Archaeology can only be traced back to about 1600 years ago, that is, in the middle of Shang dynasty, and it is impossible to prove the existence of Xia dynasty. The so-called five thousand years is to include the legendary era and round it up to an integer.