1.)Answer:In the later 20th century, ideas were refined along with data accrual, and migration and acculturation were seen as the methods whereby Indo-Aryans and their language and culture spread into northwest India around 1500 BCE. The term "invasion" is only being used nowadays by opponents of the Indo-Aryan Migration theory.
2.)The migration into northern India was not a large-scale immigration, but may have consisted of small groups which were genetically diverse. Their culture and language spread by the same mechanisms of acculturalisation, and the absorption of other groups into their patron-client system.
Explanation: That Should Be My Awnser Cause I Did Study About This :)