Tamaz V. Gamkrelidze

"The Common Indo-European word for 'beaver', *bi»ibher ~ *bi»ebher, preserves an original meaning 'brown' or 'shiny' in some of the dialects which lack it in the meaning 'beaver'. The word is attested in the Rigveda in the sense 'red- brown' (of horses, cows, gods, plants), Ved. babhrú-; in Mitannian Aryan bapru-nnu is a horse color (Mayrhofer 1966:137ff., 1974:§7); the non-reduplicated cognate is a horse color term in Slavic: Pol. brony 'bay', OCzech brony 'white', ORuss. bronyi 'white'. In later Sanskrit the term refers to a specific animal, the ichneumon (Herpestes ichneumon, a long-tailed species of mongoose that kills otters and mice). In Greek the non-reduplicated cognate means 'toad', which is consistent with the meaning of Old Prussian brunse 'roach; small fish', Lith. dial. bruñSé (Toporov 1975-:I.256-57)... In summary, derivatives of *wot'or- 'water' mean 'otter', and reduplicated derivatives of the color term mean 'beaver', only in a sharply limited dialect group which includes the later European dialects (Baltic, Slavic, Germanic, Italic, Celtic) and Avestan. This is apparently an innovation, one having to do with the particular ecological environment inhabited by speakers of these dialects. It is notable that the Indo-Iranian languages are split by this isogloss: Sanskrit shows the more archaic situation, while Avestan displays the innovation."

"According to the Gamkrelidze and Ivanov model, this protolanguage initially contains two major dialect groupings, which they call A and B. Group A consists of Anatolian, Tocharian, and Italic-Celtic, group B, of Indo-Aryan, Greek, Armenian, Balto-Slavic, and Germanic. Anatolian, which is held to have uniquely preserved some very archaic language features as I have discussed, is the first to break away from the home-land, leaving the rest of group A and group B together for a period during which they develop some common isoglosses not visible in Anatolian. Many scholars hold that Tocharian was the next to break off. After the initial departure of Anatolian, and Tocharian group A my parts company with group B and eventually subdivides into the Celtic and Italic language groups that enter into protohistory. After being separated from group A, several isoglosses in group B require that Indo-Iranian, Greek, Germanic, and Balto-Slavic all coexisted in some degree of proximity. Subsequently this group also subdivides into Balto-Slavic-Germanic and Indo-Iranian-Greek-Armenian, but in such a way that Indo-Iranian maintains a central position for a period. This centrality allows it to share isoglosses with Slavic, on the one hand, and Germanic, on the other, even while remaining more closely affiliated with Greek and Armenian. Balto-Slavic-Germanic also goes its separate way in time, and the remainder of group B, having developed some common features among its members, also eventually breaks down into the individual Indo-lranian, Greek, and Armenian groups that ultimately manifest in the historical record. These morphological isoglosses separating the various groups are further reinforced by phonemic and lexical isoglosses, which are "unambiguous evidence for the historical reality of the dialect areas of Indo-European" (Gamkrelidze and Ivanov 1995, 364)."