What reasons might be behind the development of the caste system in India?

According to one long-held theory about the origins of South Asia's caste system, Aryans from central Asia invaded South Asia and introduced the caste system as a means of controlling the local populations. The Aryans defined key roles in society, then assigned groups of people to them. According to this theory, the caste system began with the arrival of the Aryans in India. The Aryans arrived in India around 1500 BC. The fair skinned Aryans arrived in India from south Europe and north Asia. ... When the Aryans arrived in India their main contact was with the Dravidians and the Austroloids.

The majority of both parties voted in favor of the bill all senate republicans voted in favor of the bill