Archaeology
The Andronovo, BMAC and Yaz cultures have been associated with Indo-Iranian migrations, with separation of Indo-Aryans proper from Proto-Indo-Iranians dated to roughly 2000–1800 BC. The Gandhara Grave, Cemetery H, Copper Hoard and Painted Grey Ware cultures are candidates for subsequent cultures associated with Indo-Aryan movements, their arrival in the Indian subcontinent being dated to the Late Harappan period.
It is believed Indo-Aryans reached Assyria in the west and the Punjab in the east before 1500 BC: the Hurrite speaking Mitanni rulers, influenced by Indo-Aryan, appear from 1500 in northern Mesopotamia, and the Gandhara grave culture emerges from 1600. This suggests that Indo-Aryan tribes would have had to be present in the area of the Bactria-Margiana Archaeological Complex (southern Turkmenistan/northern Afghanistan) from 1700 BC at the latest (incidentally corresponding with the decline of that culture).
Read more about this topic: Indo-Aryan Migration