Bhutan’s prehistoric period, of which there is neither ethnic, paleobotanic, geographic, or physiographic record, fell roughly between 500 B.C. & A.D. 500. Fire, earthquake, flood, & internecine warfare unfortunately destroyed whatever records may once have existed. The accidental burning in 1832 of the Dzong (monastery-fortress) in Punakha, at that time one of the capital of Bhutan, & the widespread destruction caused at the same site by an earthquake in 1897 were especially responsible for the destruction of Bhutanese historical documents relating to the period. However, a number of stones tools & megaliths available suggest that Bhutan was populated from a relatively early date, probably around 2000-1500 B.C.
Little is known about the early history of Bhutan. From the available artifacts preserved in a small number of ancient monasteries, we find that Bonism, shamanistic ritual, was followed in Bhutan prior to the advent of Buddhism. The Bon tradition & ritual are still practiced in some parts of Bhutan during the celebration of local festivals.