While this does not imply that a full-fledged caste system had come into being in Rig Vedic times, the four-fold division of society into varnas did exist, which became a fairly rigid caste system by the time of the Manusmriti .
The role of the Agnicayana ritual, described in the Brahamanas, was to refertilize the womb of the Creator, Prajapati (likened to the Rig Vedic cosmic male), and to reinsert inside of him new forms needed to render Prajapati pregnant once again.
This contribution examines the Rig Vedic terms in -pitva- (abhipitva-, apapitva-, apitva-, prapitva-, and sapitva-) by considering both their distribution among the poetic families and the juxtapositions in which the terms are employed by the bards of each book.
Since the final hymns of the first mandala represent a late layer of Rig Vedic language, it would not be surprising if the sense of prapitva- had become extended or otherwise changed from the meaning seen in earlier sections of the Rig Veda.
Questionable interpretations of all these varieties are found literally in every verse; the author sometimes seems to take even the most apparently straightforward pieces of Rig Vedic diction as a challenge to his powers of reanalysis.