The Aryans were a fair-skinned people, unquestionably of the same
general stock as ourselves. Pressing down from Central Asia through
those north-western passes where alone land-access is possible to India,
elsewhere impregnably guarded by the mountain wall of the Himalayas, the
Aryans subdued the dark-skinned Dravidian aborigines, and settled down
as masters. This conquest was, however, superficial and partial. The
bulk of the Aryans remained in the north-west, the more adventurous
spirits scattering thinly over the rest of the vast peninsula. Even in
the north large areas of hill-country and jungle remained in the
exclusive possession of the aborigines, while very few Aryans ever
penetrated the south. Over most of India, therefore, the Aryans were
merely a small ruling class superimposed upon a much more numerous
subject population. Fearing to be swallowed up in the Dravidian ocean,
the Aryans attempted to preserve their political ascendancy and racial
purity by the institution of "caste," which has ever since remained the
basis of Indian social life. Caste was originally a "colour line." But
it was enforced not so much by civil law as by religion. Society was
divided into three castes: Brahmins, or priests; Kshatriyas, or
warriors; and Sudras, or workers. The Aryans monopolized the two upper
castes, the Sudras being the Dravidian subject population. These castes
were kept apart by a rigorous series of religious taboos. Intermarriage,
partaking of food and drink, even physical propinquity, entailed
ceremonial defilement sometimes inexpiable. Disobedience to these taboos
was punished with the terrible penalty of "outcasting," whereby the
offender did not merely fall to a lower rank in the caste hierarchy but
sank even below the Sudra and became a "Pariah," or man of no-caste,
condemned to the most menial and revolting occupations, and with no
rights which even the Sudra was bound to respect. Thus Indian society
was governed, not by civil, but by ceremonially religious law; while,
conversely, the nascent Indian religion ("Brahminism") became not
ethical but social in character.

These things produced the most momentous consequences. As a "colour
line," caste worked very imperfectly. Despite its prohibitions, even the
Brahmins became more or less impregnated with Dravidian blood.[192] But
as a social system caste continued to function in ways peculiar to
itself. The three original castes gradually subdivided into hund