Conversation so far:
What are the origins of the Vedic period?
After the collapse of the Indus Valley Civilisation, which ended circa 1900 BCE, groups of Indo-Aryan peoples migrated into north-western India.
What were differences after groups of Indo-Aryan peoples started inhabiting the northern Indus Valley?
The Vedic period beliefs and practices of the pre-classical era were closely related to the hypothesised Proto-Indo-European religion, and the Indo-Iranian religion.

Question: What were the religious beliefs?
Self-contained rewrite: What were Vedic period religious beliefs?