The population composition by language

Nepalese are descendants of migrants from parts of earlier Greater Nepal, Tibet, India and parts of Burma and Yunnan along with native tribal population. Among the earliest inhabitants were the Kirat of east mid-region, Newar of the Kathmandu Valley and aboriginal Tharu in the malarial southern Terai region. The ancestors of the Khas (Bahun, Chhetri, Thakuri, Sanyasi, Dalit) migrated eastward along the himalayan foothills out of Kashmir, Kumaon, Garhwal-- parts of then Greater Nepal, Karnali Pradesh (Nepal) and perhaps also north from the Gangeatic Plains during invasions. Other ethnic groups trace their origins to North Burma, Yunnan and Tibet, e.g. the Gurung and Magar in the west, Rai and Limbu in the east, and Sherpa and Bhotia in the north.
In the Terai, a part of the Ganges Basin with 20% of the land, much of the population is physically and culturally similar to the Indo-Aryans of northern India. Indo-Aryan and East Asian looking mixed people live in the hill region. The mountainous region is sparsely populated above 3,000 meters, but in central and western Nepal ethnic Tibetans inhabit even higher semi-arid valleys north of the high Himalaya. Kathmandu Valley, in the middle hill region, constitutes a small fraction of the nation's area but is the most densely populated, with almost 5 percent of the nation's population. Nepal is a multilingual, multireligious and multiethnic society.