In Analysis of the 1931 Census of India Hodson analysed the physical types in India, in great detail, adopting the models dominant in his day. This analysis was independent of the castes, and Brahmins and Dalits were classified in the same "racial groups". For example, Telugu Brahmins and Chamars were classified as "Racial Element A". In total, he distinguished seven "racial elements", from A to G. Hodson used the classical "brachycephalic" and "dolichocephalic" terminology in force in racial discourses of the day. This was a typology constructed from the so-called "cephalic index" and to classify human populations according to this purported scientific measure. Invented by the anatomist Anders Retzius, the cephalic index classification was disputed by Franz Boas's anthropological works, and Boas's criticisms are widely accepted today. Hodson also typically associates racial categories with supposed stages of economic and linguistic development, implying a hierarchy of racially defined cultures, a view characteristic of scientific racism. Hodson believed that the earliest occupants of India were probably of the "Negrito race", followed by the "proto-Australoids". Later, an early stock probably of the Mediterranean race, came to India and mingled with the proto-Australoids. He believed that these people spoke an agglutinative language from which the present Austroasiatic languages are derived. They had a rudimentary knowledge of agriculture, building stone monuments, and primitive navigation. This migration was followed by an immigration of more civilised Mediterraneans from the Persian Gulf. These people had the knowledge of the metals, but not of iron. They were followed by later waves of immigrants who developed the Indus valley civilization. All these immigrants were of the dolichocephalic type, but the Indus valley people had a mixed brachycephalic element coming from the Anatolian plateau, in the form of the Armenoid branch of the Alpine race. These people probably spoke the Dravidian languages. Later, a brachycephalic race speaking perhaps an Indo-European language of the "Pisacha or Dardic family", migrated to India from the Iranian plateau and the Pamirs. During about 1500 B.C., the Indo-Aryans migrated into Northern India.
