The areas covering Hoang-Ho and Yang-tse - kiang rivers to the north-west China on the east, the entire Brahmaputra Valley on the west, Tibet on the north and Patkai mountains on the south were predominantly inhabited by the present so-called Indo-Mongoloid people in the ancient times. These Mongoloid people were, no doubt, the Kiratas in those old times as mentioned in Ramayana and Mahabharata. In the later periods, numerous ethnic groups of people had sprouted from those Kiratas. These vast tracts of the north-east India were the land of early settlement of the Mongoloid people in India under the name of Kirata. It may rightly be pointed out that the land of Kiratas once extended up to the Punjab in the west. According to Dr. Sunity Kumar Chatterjee, ancient Assam and its eastern frontiers were adjacent to the south-eastern China and the Kirata country comprised Tibet, Sikkim, Bhutan, Manipur and adjacent areas of these vast tracts of North-East India.
The most important ethnic group of the Kiratas or the Mongoloid people was evidently the Bodo group. B.K.Barua writes that the most important group of tribes of the Tibeto-Burman race known as Bodo formed the numerous and important section of the Non-Aryan peoples of Assam and they built strong kingdoms and with various fortunes and under various tribal names, - the Chutiya, the Kachari, the Koch etc. held sway over one or another part of Assam during different historical times.
  
Here it is endeavored to give an overview of the social history of the Bodos in ancient times. The legendary events reflected in the epics and in other ancient books like 'Srimadbhagavad', 'Purnas' etc. focus the genealogy of Bana, a famous Bodo king contemporary to Lord Krishna. The predecessors of king Bana may be traced to Joy-Bijoy who once lived with Lord Vishnu in heaven. But, as ill luck would have it, they had to take rebirth as 'Asuras' on this earth in the womb of Diti by the unexpected curse of Seer Sanat Kumar and his three younger brothers, who were the sons of Lord Brahma. Diti was the daughter of Dakskya and wife of Seer Kashyapa, the son of Seer Marishi. Joy-Bijoy took rebirth in the womb of Diti by the names of Hiranyanakshipu and Hiranyanakshya respectively and both of them were again taken to heaven by Lord Vishnu by means of killing them by Boar incarnation and Man-lion incarnation.