Is it possible that Indo-European as a branch of Uralo-Altaic was transformed under the influence of a Caucasian substratum regarding sredni stog?
Gimbutas (1985: 191) has suggested that the Srednij Stog II culture in the DnieperDonets region which she identifies as her Kurgan I and II cultures (ca. 4500–3500BCE) was not the result of local evolution in that region but had its source in an
intrusion from an earlier culture farther east with connections to the earliest Neoli-thic in the Middle Urals and Soviet Central Asia. The archaeological record of the regions still farther east before that time is unfortunately still largely blank.:Edwin G. PulleyblankUniversity of British [email protected] PEOPLES OF THE STEPPE FRONTIER IN EARLYCHINESE SOURCES*
...the linguistic evidence from our family does not lead us beyond Gimbutas’ secondary homeland and that the Khvalynsk culture on the middle Volga and the Maykop culture in the northern Caucasus cannot be identified with the Indo-Europeans. Any proposal which goes beyond the Sredny Stog culture must start from the possible affinities of Indo-European with other language families. It is usually recognized that the best candidate in this respect is the Uralic language family, while further connections with the Altaic languages and perhaps even Dravidian are possible... What we do have to take into account is the typological similarity of Proto-Indo-European to the North-West Caucasian (i.e. Adyg) languages. If this similarity can be attributed to areal factors, we may think of Indo-European as a branch of Uralo-Altaic which was transformed under the influence of a Caucasian substratum. It now appears that this view is actually supported by the archaeological evidence. If it is correct, we may locate the earliest (Uralo-Altaic) ancestors of the speakers of Proto-Indo-European north of the Caspian Sea in the seventh millennium. [F.Kortlandt, Journal of Indo-European Studies, Volume 18, 1990, p.131]
There is now a consensus of linguists and mythologists that the Indo-European linguistic family is closest to the Finno-Ugric. The Indo-Uralic hypothesis, whereby the Indo-European family is classed with the Uralic-Yukaghir, Altaic, and others, is particularly strong (Anttila 1972). [M.Gimbutas, Current Anthropology, Volume 27, Issue 4 (Aug. - Oct., 1986), p. 306]