The theory of a southern origin (to which a further serious objection will be stated presently) implies a gradual infiltration of Chinese immigrants through South or Mid-China (as above indicated) toward the north, but there is little doubt that the movement of the races has been from north to south and not vice versa. In what are now the provinces of Western Kansu and Ssŭch’uan there lived a people related to the Chinese (as proved by the study of Indo-Chinese comparative philology) who moved into the present territory of Tibet and are known as Tibetans; in what is now the province of Yünnan were the Shan or Ai-lao (modern Laos), who, forced by Mongol invasions, emigrated to the peninsula in the south and became the Siamese; and in Indo-China, not related to the Chinese, were the Annamese, Khmer, Mon, Khasi, Colarains (whose remnants are dispersed over the hill tracts of Central India), and other tribes, extending in prehistoric times into Southern China, but subsequently driven back by the expansion of the Chinese in that direction.