Namit Arora at Shunya’s Notes:
How the institution of caste took root and spread is still a hotly debated question among scholars, but its story begins c. 1500 BCE with the arrival of the Indo-Aryans into what is now Pakistan. Data from disciplines like linguistics, philology, and archaeology strongly suggests that these bands of nomadic pastoralists came from further west. Upon arrival, they encountered long settled rural communities, which were perhaps divided into subgroups based on occupation, much like guilds—in the sense that the subgroups were not hierarchical, hereditary, or endogamous. The Indo-Aryans, whose culture became dominant, introduced into the region their social pyramid with three classes, or varnas: the Brahmins (priests and teachers), the Kshtriyas (warriors and rulers), and the Vaishyas (traders and merchants). They added a fourth varna after their arrival: the Shudras (laborers and artisans). All four varnas appear in the earliest known Indo-Aryan text, the Rig Veda, and were no doubt a feature of the emerging Vedic society.
As the settled indigenous communities became part of the early Vedic society, they also adopted its principle of hierarchy, turning their own occupational subgroups into castes, or jatis. The principle of hierarchy, proposed Dumont, had to do with ritual ‘purity’ and ‘pollution’ that members of each occupational subgroup were assigned at birth. The highest ‘purity’ points went to those with religious, intellectual, and administrative pursuits, the lowest to workers associated with dead bodies, human waste, tanneries, butchery, street cleaning, and such—most of these were in fact deemed too low to be part of the varna system at all, i.e., they were considered outcastes. Stated differently, ‘purity’ became a means of codifying social power relations using Brahminical ‘knowledge’. More:
