From around the 8th century, areas on the northern frontier of the Kirat region began to fall under the domination of migrant people of Tibetan origin. This flux of migration brought about the domination by Tibetan religious and cultural practices over ancient Kirat traditions. This influence first introduced shamanistic "Bön" practices, which in turn were later replaced by the oldest form of Tibetan Buddhism. The early influx of Bön culture to the peripheral Himalayan regions occurred only after the advent of "Nyingma", the oldest Buddhist order in Lhasa and Central Tibet, which led followers of the older religion to flee to the Kirat areas for survival. The Tibetan cultural influx ultimately laid the foundation for a Tibetan politico-religious order in the Kirat regions, and this led to the emergence of two major Tibetan Buddhist dynasties, one in Sikkim and another in Bhutan. The early political order of the Kingdom of Bhutan had been established under the political and spiritual leadership of the lama Zhabs-drung "Ngawang Namgyal".