Racial Theory of Caste:
Herbert Risley is one of the ardent advocates of racial theory of the origin of caste system. Other supporters of this theory are the scholars like Ghurye, Majumdar, Westermarck and others. According to this theory, caste system came into existence due to clash of cultures and the contact of races. The Aryans came to India as conquerors, because of their better complexion, physical appearance and built up of the body. In comparison with the non-Aryans, the Aryans placed themselves as a superior race over the non-Aryans. Thus the Aryans considered the natives as inferior to them and maintained their own ideas and ceremonial purity. The Aryans got married to the non-Aryan women, but refused to give their own daughters in marriage to the non-Aryans. The Chandals had the lowest position in society. Thus the irregular union between races and racial superiority were held responsible for the origin of caste system in India.

Risley has mentioned six processes of development of caste system.

(a) Changes in traditional occupation: When a caste or a sub-caste changes its traditional
occupation and adopts a different one, it ultimately develops into a distinct caste.

(b) Migration: In the past the transport and communication system was not developed. Therefore whenever a section of caste migrated from one region to the other, it faced
difficulties in maintaining contacts with the earlier place.

(c) Customary changes: From the earliest times, the formation of new castes was based on the rejection of old custom and usages and acceptance of the new practices and habits.

(d) Preservation of old practices: Some caste groups are interested in maintaining their old traditions and on those bases they separate themselves from the rest of society who follow relatively new customs and traditions. The caste groups preserving old patterns may take up new names.

(e) Getting into the folds of Hinduism: Certain tribes or the section of the tribes enter into
the rank on Hinduism by changing their lineage, by accepting the tenets of any school of Hindu religion, by joining Hindu religion and by establishing relations with the Hindus without changing its name. Thus, the tribes transform themselves into castes. The examples of the Rajbanshies of Bengal and Muria Gonds of MP may be taken in this regard.

(f) Role of religious enthusiasts: Separate sects are created by the religious enthusiasts. They preach their doctrines and attract people towards them. Gradually, their
followers develop into a new group. Kabir may be taken as an example in this regard.