The caste system in India as practiced today has several layers of complexities, mostly undesirable ones. But it's a reality. Now, it's commonly accepted that the Indus Valley civilization involved people from parts of present day Europe. I am trying to understand if this practice has origins elsewhere or if the caste system has it's origins in this sub-continent itself.
An alternative way to put my query is: What, if any, is the earliest evidence of a practice similar to the caste system in the world?