Mitanni (1500-1300 BC) in upper Mesopotamia (northeastern Syria). The
Mitanni rulers in a treaty, 1380 BC, prayed to the gods Mitra, Varuna, Indra
and the Nasatyas of the Rigveda. There is such closeness between the
surviving Mitanni words and the language of the Rigveda that there might not
have been any great distance in time or space between the Mitanni and their
separation from the main body of Indo-Aryan speakers. The separation
possibly took place not before 2000 BC and in a region not much beyond
eastern Iran. Since the Mitanni shared with the Rigveda composers a deep
interest in horses and chariots, the presence of the true domesticated horse
should be the one necessary marker for the presence of their common
(linguistic) ancestors in the archaeological record.
Rigvedic Language If the Indo-Aryan speakers migrated to Swat and Pirak
before 1500 BC, the time was not far off when they would move into the
Punjab. Possessing horses and chariots, they would have a decisive advantage
over their eastern foes, who still had only ox-carts (to judge from the
terracotta figurines of Cemetery-H and Late Harappan cultures. The Rigveda
exhibits such familiarity with the Suvastu (Swat) river and most of
Afghanistan that we have to assume that after Indo-Aryan speech spread into
the Punjab, linguistic unity was maintained between the borderland and the
Punjab for quite some time. This kind of expansion of Indo-Aryan speech
necessarily involved the migration of a significant number of people from the
borderland, into the Indus plains. But, at the same time, the migration might
not have been on such a massive scale as to leave its imprint on the genetic
complexion of the region. Moreover, since the Indo-Aryan speakers had
settled in these areas for some time previously, they must have already mixed
with populations which, being neighbours to the Indus people, were not
probably biologically much different from the latter.
                         ORIGIN OF PRAKRITS
  Another set of languages which were neither Dravidian nor Austro-Asiatic
  have also probably provided some non-Indo-European words to the
  Rigveda and early Sanskrit. Interaction with such languages in
  Afghanistan (like Nuristani) probably started much before the Indo-Aryan
  speakers reached India, and might      have caused the early appearance of a