We don’t exclude the possibility of contacts between the ancient Indo-Europeans and their Caucasian contemporaries, but no precise trace has so far been brought forward. The structural similarities that one may envision for a very distant period would not imply a common origin nor a period of symbiosis.

Martinet, André, 1986: Des Steppes aux Océans. L’Indo-Européen et les “Indo-Européens”, Paris: Payot. Martinet (1985:21):, quoted in Elst, Koenraad (2018). Still no trace of an Aryan invasion: A collection on Indo-European origins, and in Elst, "Some unlikely tentacles of early Indo-European", published as ch.3 in Angela Marcantonio & Girish Nath Jha, eds.: Perspectives on the Origins of Indian Civilization, Center for Indic Studies, Dartmouth MA, and DK Printworld, Delhi, 2013, from Dartmouth conference 2011.