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.

What would cause the proto-Aryans to move, and in so many directions, to Europe, the Middle East and India? Generally when groups migrate it is in one direction. People do not abandon their homelands and move in all directions with such fury without a reason, particularly nomadic people who are wedded to their territory.

How could the primitive Aryans have been so successful in conquering the civilizations of the world from Greece to India, as well as imposing much of their culture, or at least language, on older and more sophisticated civilizations? Language, after all, is the most difficult aspect of culture to change. Many countries, for example, Europe under Christianity or Iran and Pakistan under Islam, have changed their religion but not their language. How could the primitive Aryans be so successful at doing this, when they were not only less sophisticated but less numerous than the peoples they overran as well as illiterate?

We should note that Afghanistan is not an easy place to cross through even today. Even Alexander lost most of his army trying to cross this region by land. How could sufficient numbers of people have done it in ancient times so as to overwhelm the existent population of north India. In the historical period armies from Central Asia have been able to conquer north India at times. But they have not been able to change the population or to impose their language on the subcontinent. How could disorganized nomads, such as the Vedic people were supposed to have been, accomplish this and also remove any record or memory of what they had done?

To assume that the proto-Aryans were just simply vicious and had to ruthlessly conquer everyone, that with some advantages like the use of the horse they were able to do so, does not work either. Such vicious conquests cause tremendous resistance in the conquered people which is not in evidence in ancient India, Greece or elsewhere where the Aryans have been found. The ancient Indo-European peoples did not have a reputation as being as being particularly cruel. In the ancient Middle East of the second and first millennium BC, for example - in which a number of Indo-European peoples existed like the Hittites, Mittani and Kassites - the reputation for cruelty did not go to them but to the Semitic Assyrians against whom they fought. While the Assyrians and Babylonians enslaved the Jews, it was the Persians, who called themselves Aryans, who released them from their captivity! In any case, no evidence of such movement of populations into India or destroyed cities has been found.