"The structure of the text has been more extensively studied, already by Bergaigne (1878-83) and Oldenberg in the 19th century. From the latter's Pro… - Michael Witzel

“The Indo-Aryan influence, whether due to actual settlement, acculturation, or, if one prefers, the substitution of Indo-Aryan names for local ones, was powerful enough from early on to replace local names, in spite of the well-known conservatism of river-names. This is especially surprising in the area once occupied by the Indus civilization, where one would have expected the survival of earlier names, as has been the case in Europe and the Near East. At the least, one would expect a palimpsest, as found in New England, with the name of the State of Massachussetts next to the Charles River formerly called the Massachussetts River, and such new adaptations as Stony Brook, Muddy Creek, Red River, etc. next to the adaptations of Indian names such as the Mississippi and the Missouri. The failure to preserve old hydronomes even in the Indus Valley (with a few exceptions noted above) indicates the extent of the social and political collapse experienced by the local population.” (p 107)

“It must be underlined that just like an ancient inscription, these words have not changed since the composition of these hymns c.1500 BCE, as the RV has been transmitted almost without any change […] The modern oral recitation of the RV is a tape recording of c.1700-1200 BCE.” (WITZEL 2000a:§8).

“in northern India, rivers in general have early Sanskrit names from the Vedic period, and names derived from the daughter languages of Sanskrit later on.” (p 105)