1. In the late 19th/early 20th century, British colonial administrators like Herbert Hope Risley developed racist theories to differentiate and categorize Indian castes and tribes, including the notion of Aryan and Dravidian races. 2. Risley used pseudoscientific measures like nasal indexes to develop a racial taxonomy and imposed a caste hierarchy through the Indian census. 3. Scholars like Ambedkar later debunked Risley's theories by showing data did not support differences between castes. However, the British entrenched caste in government and society.