Explanation:

The earliest settlers were Mon-Khmer speakers (currently identified with the Khasi and Pnar people) (Wave 1) originating in Southeast Asia. These people settled in the foothills but were pushed up into the hills (Khasi Hills, Garo Hills, and Karbi Anglong and North Cachar Hills) by different Tibeto-Burman speakers (Wave 2) migrating from Tibet and South China. These people are today identified as the Monpa and Sherdukpen peoples of Bhutan and Arunachal Pradesh; the Mishings and Deuris of Upper Assam; the Bodo-Kachari people scattered all over Assam; the Tiwa (Lalung) and Rabha peoples in East Assam; Sonowal Kacharis and Thengal Kacharis in Upper Assam and Dimasa people in Dima Hasao district.