 Smelser and Lipset propose in their review of Hutton's study of caste system in colonial India the theory that individual mobility across caste lines may have been minimal in British India because it was ritualistic.They state that this may be because the colonial social stratification worked with the pre-existing ritual caste system.The emergence of a caste system in the modern form, during the early British colonial rule in the 18th and 19th century, was not uniform in South Asia.