It is a basic tenet of migration and homeland theory that the geographical location of a language family’s proto-homeland is to be sought in the vici… - Johanna Nichols

Three language trajectories are shown.., and these are contemporaneous but not equal in prominence or carrying power. The central one, henceforth the steppe trajectory, shows the east-to-west spread of languages across the Eurasian steppe, and is based on four spreads: that of IE to Europe in the Bronze Age, that of Iranian to (and occasionally into) Central Europe during the Iron Age, that of Turkic in the early centuries of this era, and that of Mongolian beginning in the Middle Ages. To the north of it is the almost equally extensive forest trajectory through the northern forests. This is the route followed by the Uralic language family in its spread from the central Urals (c. the fourth or fifth millennium) as far west as Norway and Estonia (by perhaps the first millennium BC). To the south of the Caspian and Black Seas runs the southern or desert trajectory that brought the Mongols to the southern Caucasus, and before that Turkish to Turkey, and before that Iranian languages to ancient Persia and northern Mesopotamia, and still earlier Armenian, Hittite and its sisters, and other early IE dialects to Asia Minor.

The Iranian family, which was next to sweep across the steppe and deserts, finds its region of greatest diversity in the central Asian mountains, and its ancestral Indo-Iranian family finds its own greatest diversity in the mountain region from central Asia to northern India (i.e. Bactria- Sogdiana and parts just south).

The location of the Anatolian branch of IE (Hittite and its sisters) is a problem, or at least a puzzle, for IE homeland studies. The Anatolian languages are attested very early in Asia Minor, removed from Europe and far from the steppe; Gamkrelidze and Ivanov ... offer as a strength the ability of their proposed homelands to account for the location of Hittite with minimal migration. Alternatively or additionally, the location of Tocharian—attested in the early centuries AD well to the east of most IE territory in present-day Xinkiang (Chinese Turkestan)—is a problem or a puzzle... Accounting for the locations of both Hittite and Tocharian is usually presented, at least rhetorically, as a major problem.