The Aryan invasion theory was invented to solve the riddle of languages. However the invasion theory itself is filled with problems. We could say that the Aryan invasion theory is an attempt to solve one riddle by postulating another.
If such an invasion did occur, what would have caused it? Central Asia is not a very favorable region for producing populations even today, as we have already noted. How could it produce the populations necessary to overrun not only India but much of the Middle East and Europe. Ancient India was not uninhabited. After the long urban Harappan age it was highly populated at the time of the proposed invasion. Such populations could not have easily been overwhelmed, forced to move or be assimilated. After all it was not an organized conquest but a random movement of tribal peoples which is postulated for the Aryans.
Author : David Frawley