The original civilizations of the indus valley were greatly changed by the migration of the

Aryan migration

Explanation:

The Indus valley civilization originally inhabited by the Aryan civilization and has been proved by the architecture of the buildings and the artifacts that have been found at the place. And they have known to be originated in the 1800-1500 BC and had migrated to the India and settled in the Indus valley Gangetic plain and spoke the indo European languages.

"pacesetter of the south," comma inside the quotes

Answermost of the time it would be ground into fine sediment,and sometimes they are carried away from the original location;