In this religious-social system of inequality, we can see the basis for rebellion.
As it turned out, towards the end of the Vedic era (6th century BCE), a new movement rose that rejected the authority of the Vedas, the Brahmins, the Sanskrit scriptures, and the rules for human conduct that that ancient doctrine had entailed.
This movement started among forest-dwelling ascetics, collectively known as the śramaṇas (shramanas). These wandering ascetics historically developed into Jainism, Buddhism, and some smaller traditions that are no longer around.