In the pre-colonial era, social identities were more malleable. This indicates that the caste system was a colonial construct.
Pre-colonial documents indicate that prior to the arrival of the British, social identities were far more fluid. Moving towns allowed families to achieve significant social mobility, with farmers becoming soldiers, merchants, or laborers without facing any caste oppression.
Relative social mobility prior to British rule does not prove that the British created the caste system. It is possible that the caste system was already in place prior to the British arrival, but had a lesser impact on social mobility. In this case, the British could not be attributed with inventing the caste system but may have played a role in rolling it out across the country or manipulating it to suit their purposes.
[P1] The caste system restricts social mobility. [P2] Prior to the colonial period, India enjoyed far more social mobility. [P3] Therefore, the British created the social barriers that came to define Indian society. [P4] Therefore, the British colonial powers invented the caste system.
Rejecting the premises
[Rejecting P4] The British didn't invent the caste system, they merely modified the existing caste system.