"The fact that proto-Aryan *ai and *au are replaced in Indo-Aryan by e and o, while in Iranian they are preserved as ai and au and that ai and au regularly appear on the Anatolian documents (eg. Kikkuli‘s aika), is unfortunately inconclusive. It is quite possible that at the time of our oldest records (the hymns of the Rigveda) the actual pronunciation of the sounds developed for *ai and *au spoken and written by the tradition as e and o, was still ai and au. The e and o can be a secondarily introduced change under the influence of the spoken language or the scholastic recitation."