NOTES

Ans.
The commonly proposed period of earlier Vedic age is dated back to 2nd millennium BCE.[8] After the collapse of the Indus Valley Civilisation, which ended c. 1900 BCE,[9][10] groups of Indo-Aryan peoples migrated into north-western India and started to inhabit the northern Indus Valley.[11][note 3][note 4]
The knowledge about the Aryans comes mostly from the Rigveda-samhita,[24] which was composed between c. 1500–1200 BCE.They brought with them their distinctive religious traditions and practices. The Vedic beliefs and practices of the pre-classical era were closely related to the hypothesised Proto-Indo-European religion,[28][29] and the Indo-Iranian religion.According to Anthony, the Old Indic religion probably emerged among Indo-European immigrants in the contact zone between the Zeravshan River (present-day Uzbekistan) and (present-day) Iran.It was "a syncretic mixture of old Central Asian and new Indo-European elements", which borrowed "distinctive religious beliefs and practices"from the Bactria–Margiana Culture.At least 383 non-Indo-European words were borrowed from this culture, including the god Indra and the ritual drink Soma.