How did south asia become more integrated despite the absence of an imperial state?

In the beginning, the Vedic people were all very similar in rank, but as they started to disperse and spread out across South Asia they became more involved in agriculture which caused some problems socially. As agriculture became more and more important, the Vedic people began to argue as to who was more important: the landowners or the land workers. To show the differences between the two, a caste system was created. The caste system was divided among four different castes, and it was called varna. First was the Brahmans, who were the most powerful people out of all the castes. The Brahmans were priests, and they gained their high rank in the system by being able to communicate with the deities and perform rituals. Next in line, were the Kshatriyas, who were the people who had a lot of power and handled the land. Following them were the Vaishya, or the householders whose job it was to manage the land and take care of the livestock. However, as the work became harder and harder to do people of the Vaishya caste would often hire people to do their work for them or use slaves. These people were known as the Shudras. The Shudras consisted of the slaves and menial laborers.