Which group introduced and developed the caste system in india

Caste system was not intentionally introduced by a specific group. It came into existence naturally similar to class system in modern world. Those who were teachers, scholars, priests were considered respectable by all and thus made into a higher caste, on the other side, the sweepers and cleaners, whose work was considered filthy and unworthy naturally formed a low caste group.

This category is called mala in se crimes