Which of the following statements about the social structure of the Sangam Age is not correct?

Sangam literature mentions three regular varnas, namely, Brahmins, Kshatriyas and Vaisyas

There were four castes, namely, Tudiyan, Panan, Paraiyan and Kadamban

People were organized in professional social groups living apart from one-another

The difference in the status and economic conditions was well accepted and rarely challenged by the people