Regarding distribution of castes in the entire population - it is of no interest. We are speaking only of the institutes - IISc, ISRO, DRDO and that it is skewed with Brahmins and SC/ST. Additionally, existence is not same as power/ influence. I can bet the environment looks better at any of the IITs or RECs. That should suffice as a response.
Please follow up offline (Again I think u joined yesterday just to fire this debate with no info on profile) if u do want to fire a debate or do some follow up or walk into IISC or ISRO. I think HN is not a right place.