Why do scholars reject the idea of a single Indo-Aryan invasion of India?

Modern scholarship has largely moved away from the term "Indo-Aryan invasion" in favor of describing a gradual "Indo-Aryan migration". Scholars reject the invasion model for several key reasons:1

• Lack of Archaeological Evidence: There is no definitive archaeological proof of a violent conquest or invasion of the Indus civilization by incoming groups. The decline of the Indus cities is now generally attributed to other factors, and there is a high degree of physical continuity between Harappan and post-Harappan societies.23
• Nature of the Movement: Evidence suggests a series of migrations or a continuing spread of Indo-Aryan speakers over several centuries rather than a single, sudden event. This process involved growing cultural interaction and integration between the newcomers and the native population, eventually leading to a new cultural synthesis.312
• Alternative Theories: Some scholars argue that Indo-Aryan culture was an original element of pre-Vedic India rather than an external import. While this remains controversial, the absence of clear physical signs of conquest has led many to favor models of migration and cultural exchange over the older, discredited invasion theory.23