It is certain ... that the Rigveda offers no assistance in determining the mode in which the Vedic Aryans entered India., .. If, as may be the case, … - A. Berriedale Keith

...the Vedic index. This book is an encyclopedia of historical and sociological knowledge extracted by study of the Vedic texts. It is based on a thorough review of Orientalist research, including especially the work of German Orientalists, but it is at the same time very much a British reading of the Vedic texts and the Orientalist interpretation of them.

By taking the linguistic evidence too literally one could conclude that the original Indo-European speakers knew butter, but not milk; snow and feet but not rain or hands!

The same terms are applied indifferently to the human enemies of the Aryans and to the fiends, and no criterion exists by which references to real foes can be distinguished in every case from allusions to demoniacal powers." "Individual Dasas" whom Keith picks out as human examples "are Ilibica, Dhuni and Chumuri, Pipru, Varchin , and Cambara, though the last at least has been transformed by the imagination of the singers into demoniac proportions".