Indo-Aryan migration
Historians have analysed the Vedas to posit a Vedic culture in the Punjab region and the upper Gangetic Plain. Most historians also consider this period to have encompassed several waves of Indo-Aryan migration into the Indian subcontinent from the north-west. The peepal tree and cow were sanctified by the time of the Atharva Veda. Many of the concepts of Indian philosophy espoused later, like dharma, trace their roots to Vedic antecedents.