Herbert Risley, a British colonial official, was the main proponent of the dominant view on the relationship between race and caste. He believed that human beings could be divided into distinct races on the basis of physical characteristics such as the circumference of the skull, length of the nose, and volume of the cranium.

Risley argued that India was a unique 'laboratory' for studying racial types because caste strictly prohibits inter-marriage among different groups. His main argument was that caste must have originated in race. He suggested that higher castes approximated Indo-Aryan racial traits, while lower castes seemed to belong to non-Aryan aboriginal, Mongoloid or other racial groups. The lower castes were believed to be the original aboriginal inhabitants subjugated by an Aryan people.

G.S. Ghurye, in his book Caste and Race in India (1932), provided a detailed critique of Risley's theory. He did not disagree with the basic argument but believed it to be only partially correct. He pointed out the problem with using averages alone without considering the variation in the distribution of measurements for a given community.

Ghurye believed that Risley's thesis of upper castes being Aryan and lower castes being non-Aryan was broadly true only for northern India. In other parts of India, the inter-group differences in anthropometric measurements were not very large or systematic. This suggested that in most of India except the Indo-Gangetic plain, different racial groups had been mixing with each other for a very long time.

Thus, Ghurye concluded that 'racial purity' had been preserved due to the prohibition on inter-marriage only in 'Hindustan proper' (north India). In the rest of the country, the practice of endogamy may have been introduced into groups that were already racially varied.