This book is the English version of the same authors New Research on the Ancient Clan. A New Examination of the Ancient Clan was published by Zhonghua Book Company in 2000 and republished by the Commercial Press in 2012. The discovery of Tocharian documents and the study of Tocharian and related historical and geographical issues are not only major events in the field of comparative historical linguistics, but also in the academic field of Central Asia. From the end of the nineteenth century to the beginning of the twentieth century, among the fragments of ancient documents unearthed in Northwest my country, some were written in an unknown language at that time, one of which was Tocharian. It poses a series of questions for linguists and historians to interpret. In particular, it must be explained clearly: No matter where the Tocharian-speaking ethnic group originated, since it came to China very early, it should leave its footprints in Chinese history. In other words, under what name did they appear in Chinese historical records? This book is the authors outline of the emigration process of the Wu family, Tao Tang family, and You Yu family based on historical materials, and constructs a hypothesis about the origin of the Sai Zhong tribes. Ed.