The theory of Aryan invasion/migration has been a prevalent explanation for the downfall of IVC and the rise of the Vedic culture. According to this theory, a group of nomadic Indo-European speaking people known as Aryans migrated from Central Asia into South Asia around 1500 BC. They brought their own culture, language and religious practices which gradually merged with the existing IVC culture, leading to the formation of Vedic civilization.
However, this theory has been challenged in recent years due to lack of substantial archaeological evidence to support it. An alternative theory, known as the Indigenous Aryan Theory, suggests that the Vedic civilization evolved from within the IVC itself, without any major external influence. According to this theory, the Vedic culture emerged from the interaction between different groups within the IVC and the development of new religious and cultural practices.