 By the 1880s, his ideas had been adapted by racist ethnologists.For example, as an exponent of race science, colonial administrator Herbert Hope Risley (1851 – 1911) used the ratio of nose width to height to divide Indian people into Aryan and Dravidian races, as well as seven castes.The idea of an Aryan "invasion" was fueled by the discovery of the Indus Valley (Harappan) Civilisation, which declined around the period of the Indo-Aryan migration, suggesting a destructive invasion.