The country's population of 600,000 is composed of three main ethnic groups. The Sharchopas, who are considered to be the earliest inhabitants of Bhutan, live mostly in Eastern Bhutan and they are of Indo-Mongoloid origin. The Ngalops populate mostly Western Bhutan migrated from the Tibetan plains and are the importers of Buddhism to Bhutan. The Lhotsampas who are of Nepalese origin settled in the southern foothills of the country in the early twentieth century. This ethnic diversity of the people has resulted in numerous dialects and languages that are spoken throughout the country. Dzongkha is the National language. English is the medium of instruction in schools and is widely spoken.