The book analyzes the theory of ethnogenesis of the Bashkirs and other peoples of the Volga-Ural region, developed by the famous Russian ethnologist, corresponding member of the Russian Academy of Sciences Rail Gumerovich Kuzeev (1929-2005). The study was written on the basis of the published works of the scientist and the materials of his archive first introduced into scientific circulation. The conclusions of R.G. Kuzeev are compared with the views of other authors. According to written sources, archeology, ethnography and anthropology, the ethnic processes that took place in the Volga-Ural historical and ethnographic region during the Middle Ages are reconstructed.