During the late 3rd and the 2nd millennia BC, horse-riding herders spread probably from the Caucasian steppe into West Asia and the Iranian plateau and as far as South Asia.
They spoke Indo-Aryan, a language belonging to the Indo-European language family, of which English and most other modern European languages are also members. Most South Asians today speak Indo-Aryan languages, but these have undergone changes in their vocabulary, grammar and pronunciation due to the influence of the Dravidian languages spoken by the people of the Indus region and probably by many other groups encountered by the Indo-Aryan invaders.
It is possible to trace the spread of these invaders using clues from these language changes. The Indo-Aryans composed hymns full of references to their way of life and their surroundings, the Vedas, handed down orally for centuries. Clues in the earliest of these, the Rigveda, show their gradual spread into the north-west and the Ganges Valley.
Archaeological evidence of their spread, however, is surprisingly elusive. A number of Late Indus towns have squatter occupations with some foreign material, and there are some finds of foreign-seeming burials and objects. Some northern settlements show signs of violent destruction.
It would appear therefore that this was not a massive invasion but a series of small-scale incursions. How then did the Indo-Aryan languages come to be so widely spoken?
This was probably a process that took many hundreds of years, but one important factor is that the Indo-Aryans were a warlike people, whereas our evidence shows no sign of warfare during the preceding Indus period. It would probably have been relatively easy for bands of Indo-Aryan warriors to dominate the peaceful farmers whose lands they were invading, their language being gradually adopted by their subjects.
