My sources are the book, ‘Ancient Civilizations’, published 2006 by McGraw Hill and National Geographic, and Hinduwebsite.com
Hinduism originated with the Aryans, northern people who migrated to and conquered India about 1500 B.C. The Aryans believed in many gods and goddesses who controlled the forces of nature. We know about Aryan religion from ancient hymns and poetry, especially epics, or long poems. For centuries, the priests, or Brahmins, recited these works, and they were eventually written down in Sanskrit. Over the centuries, the Aryans borrowed religious ideas from the Indians, and this mix of beliefs eventually became Hinduism.
The Aryans also developed the caste system. A caste is a social group that someone is born into and cannot leave. The Aryans were light skinned and it is believed that they developed the caste system to control the darker skinned Indians. The Aryans were outnumbered by Indians, and the caste system kept them separate and set rules for everyone’s behavior.
The caste system was also justified by religious beliefs about purity. It was easy to justify avoiding unclean or socially unacceptable people for the reason of maintaining spiritual purity, but this evolved into stigmatizing people simply because of their birth and family lineage, and believing it was the will of God.