[An excerpt from the chapter 'The Background to Buddhism' in her book, 'Buddhism in India: Challenging Brahmanism and Caste']
Indian Brahmans as they have evolved over the centuries represent one of the most unique elites that any society has produced. They trace their origins back to Vedic times, where they were priests of the sacrifice, and it was as priests, intellectuals and possessors of the Vedas that they appear in the middle of first millennium BCE society. However, it would be a mistake to see the Brahmans, identified as a social group in the first millennium BCE, in 'essentialist' terms, as lineal descendents of Vedic priests, just as it is a mistake to take the Khattiyas as descendents of Vedic warriors or rajanyas. Both claimed purity of descent, but this was a self-serving mythologising.
Thapar has argued that Brahmans of non-Aryan origin were attested to in legends of sages such as Agasthya and Vasistha who are said to have been born from jars and of a Rig Vedic seer being described as dasiputrah or 'son of a slave' (Thapar 1984: 52). Some Pali texts, for example the Ambattha Suttanta (see Chapter 3) indicate that they may also have included illegitimate offspring of the Khattiyas. Even the Upanishads show that an occasional man of questionable birth could be accepted as a disciple and taken into the line of 'Brahmans'; for instance, in the Chandogya Upanishad, Satyakama Jabala's mother tells him, 'Darling, I do not know what lineage you belong to. I got you in my youth, when I travelled about a great deal as a servant' (Upanisads 2000: 174).