You didn't get my point. The discrimination started very slowly....remember Ram eating Shabri ke ber.....the point of Shabri's existence was the existence of lower class and the benevolence of the upper caste.
Its not that they said you are inferior and you are superior in one day and everyone went to their homes.
Look at how few practices were modified by Rishis...like having fast....it was based on science that not eating one day is good for health, but common man can easily be influenced if its added to religious practice.
Same with artificial rain making yagyas, many yagyas which were performed were based on science....but presented differently.