text: 13th to 20th centuries The Tabaqat-i Nasiri chronicle of the Islamic world contains records of an expedition by Muhammad bin Bakhtiyar Khalji into Kamrup region between Gauda and Tibet in 1205 AD and refers to the resident people as Kunch, today's Koch people, Mej/Meg today's Mech people and Tiharu as having mongoloid appearances. These people impressed the Turkic peoples who had similar features as them, like slanting eyes, snub noses, high cheek bones, yellow complexion of the Mongols and who spoke a different language than in the rest of the subcontinent.
  Following the unification of Nepal in the late 18th century, members of the ruling families received land grants in the Terai and were entitled to collect revenue from those who cultivated the land. The Tharu people became bonded labourers in a system also known as Kamaiya. In 1854, Jung Bahadur Rana enforced the so-called Muluki Ain, a General Code, in which both Hindu and non-Hindu castes were classified based on their habits of food and drink. Tharu people were categorized as "Paani Chalne Masinya Matwali", i.e. touchable enslavable alcohol drinking group, together with several other ethnic minorities. In the late 1950s, the World Health Organization supported the Nepalese government in eradicating malaria in the forests of the central Terai. Following the malaria eradication program using DDT in the 1960s, a large and heterogeneous non-Tharu population from the Nepali hills, Bhutan, Sikkim and India settled in the region.