Original sentence: First, it was the Tibeto-Burman ethnic groups which had arrived from Tibet, Yunnan and Sinchuan provinces of China who mixed with the scarcely present aboriginal Austric people like the Khasi and Jaintia.The roots of Assamese culture go back almost two thousand years when the first cultural assimilation took place between Austro-asiatic and Tibeto-Burman groups
Edited sentence: First, it was the Tibeto-Burman and Tai people ethnic groups which had arrived from Tibet, Yunnan and Sinchuan provinces of China who mixed with the scarcely present aboriginal Austric people like the Khasi and Jaintia.The roots of Assamese culture go back almost two thousand years when the first cultural assimilation took place between Tai people , Austro-asiatic and Tibeto-Burman groups