The sacrifice of horses, in fact, is in no way specific to Vedic India: only the ritual of this sacrifice is, very different from that of the funerar… - Gérard Fussman

A. Parpola is an abundant writer, but not very rational.

This is not the place to dwell on these debates, as important as they are. We will find a good overview in the very well informed and very balanced book by Edwin Bryant which, moreover, demonstrates that, all things considered, no scientific argument allows us to choose between the theses of Indian or extra-Indian origin of the Āryas and, consequently, of the Indo-Europeans... To anyone who doubts the fact that the commonly accepted opinion in the West on the origin of i-e language peoples is based primarily on an intuition that is difficult to demonstrate, I would recommend reading E. Bryant's book. We can clearly see that the debate resurfaces from generation to generation.

p. 812 Fussman G. Entre fantasmes, science et politique. L’entrée des Āryas en Inde. Annales Histoire, Sciences Sociales. 2003;58(4):779-813.