Prior to the Iranian expansion, in the early Bronze Age, IE spread to cover the entire steppe and the Danube plain (and subsequently all of Europe), with substantial speech communities also in Anatolia (Hittite and congeners) and northern Mesopotamia (surviving in Armenian) and, in all probability, coverage of much or all of western central Asia (probably by ancestral Indo-Iranian). What is historically attested of the IE spread fits closely the pattern followed later by Iranian, Turkic, and Mongolian.

“The earliest mention of Iranians in historical sources is, paradoxically, of those settled on the Iranian plateau, not those still in Central Asia, their ancestral homeland. ‘Persians’ are first mentioned in the 9th century BC Assyrian annals: on one campaign, in 835 BC,… There are no literary sources for Iranians in Central Asia before the Old Persian inscriptions (Darius’s Bisotun inscription, 521-519 BC, ed. Schmitt) and Herodotus’ Histories (ca. 470 BC). ...

A migration that is identified, however, is east-to-west: “a part of the Timber-grave tribes moved [from Uzbekistan or even the Amu Darya basin] to the North Caucasus because of the crisis; they had already begun appearing and settling in the Caucasus at an earlier time”. (p.454) [This must be the Scythian migration, which only added to the already existing Iranian presence near and beyond the Urals. Intermittently, groups of Iranians must have moved from Bactria to the Urals and even to Ukraine for more than a thousand years. (One of the later migrating tribes were apparently the Hrvat, now known as the Croats. Before migrating west and adopting the Slavic language of the Serbs, they belonged to the Harahvaita tribe in Afghanistan mentioned as tribute-payers to the Persian empire in an Achaemenid document.)]

Approximately every two millennia, then, there has occurred a spread of a language family from a locus in the eastern part of the central Eurasian spread zone to cover the steppe and central Asia, extending partially or intermittently to the Danube plain, Anatolia, and northern Mesopotamia. The loci of the historically attested spreads are near the edge of the spread zone rather than in the centre of it: the piedmont to the south (Bactria-Sogdiana) for Iranian, the north of Mongolia for Turkic and Mongolian. The trajectories of language spread run east to west along the steppe and through the desert to the Near East as shown .... To take clear and historically well-attested examples, the locus, trajectories, and range of IE must have been much like those of Iranian or Turkic. ... The placement of the locus specifically in the vicinity of Bactria-Sogdiana is justified in .... A homeland reconstructed as locus, trajectory and range removes the dilemma: a locus in the vicinity of Bactria-Sogdiana implies a spread beginning at the frontier of ancient Near Eastern civilization and a range throughout the steppe and central Asia, following the east-to-west trajectory, with occasional or periodic spreads into the Danube plain and Anatolia.

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).

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.

“in the denomination of Ariana, which became known to the Greeks after the Macedonian conquest of the eastern territories of the old Persian empire, there was obviously reflected a tradition that located the Aryan region in the central-southern part of eastern Iran, roughly from the Hindukus southwards, and that considered some of the Medes and the Persians in the west and some of the Bactrians and Sogdians in the north as further extensions of those people who were henceforth known by the name of Ariani. And this, to tell the truth, fits nicely into the picture we have been trying to piece so far. Here too, as in the passages of the Avesta we have studied from the Mihr Yast and the Zamyad Yast, the geographical horizon is central-eastern and southeastern; the northern lands are also completely peripheral, and Chorasmia, which is present only in the very peculiar position of which we have spoken in the Mihr Yast, is not included.” ...

Rather, the Iranian division of society has a similar origin as the same division in Indian society. The Iranians came from India, as Shrikant Talageri has convincingly demonstrated. Moreover, the division is a natural one, present in every society. It may be tempting to push responsibility far from you, preferably to a foreign source, but in this case the Iranian option doesn’t fulfil your wish. Their status of “foreigner” is ambiguous, given that they came from India and are one of the “five peoples” alongside the Vedic tribe, deemed to descend from the two brothers Anu c.q. Puru, two of the five sons of Yayati. Iranians are quite present in the Veda, such as through the sages Bhrigu and Cyavana.

Along the forest trajectory as well there is evidence of either an early Indie presence or undifferentiated Proto-Indo-Iranian or Proto-Indo-Aryan. Among the Indo-Iranian loans into early Finno-Ugric are some so phonologically archaic that they could well be Proto-Indo-Iranian... Iranian, but not Indo-Aryan, regularly reflects PIE s as h, so this Finno-Ugric form looks more Indie than Iranian. Abaev also cites some less well attested forms that could be specifically Indie... These borrowings would have taken place somewhere in the vicinity of the southern Ural Mountains. They were received from a steppe language and incorporated into Finno-Ugric as it began its spread along the forest trajectory. This linguistic evidence for an Indie or Proto-Indo-Iranian wave preceding Iranian on the steppe is weak but legitimate. In partial confirmation of it, Kuz’mina identifies the Andronovo culture of eastern Kazakhstan in the mid-second millennium BC as Indo-Aryan..... There is also evidence for Indo-Aryan along the steppe trajectory in the form of a set of Crimean place names which Trubač identifies as Indo-Aryan. This evidence is even weaker—place names in general have poor diagnostic value since they lack denotational meaning—but carefully researched and again legitimate. If Trubačv is right there is evidence for an Indie advance to the western steppe. Taken together, the Finno-Ugric and Crimean evidence are consistent with the assumption of a short-lived Indie or Indo-Aryan presence at the frontier of the Iranian spread on the steppe, in addition to the well-known Indie frontier in northeastern Mesopotamia and India.

The Iranians may have been an offshoot from India.

A much more convincing theory than that of the western Iranians having emigrated from North to South across the Caucasus is that of a slow, progressive East-West emigration, a gradual penetration as it were, over the centuries, from the end of the 2nd millennium to the first half of the 1st millennium B.C. ...

We may therefore hold this proposition firmly established , that Iran or Persia in its largest sense, was me true center of languages, and of arts; which, instead of travelling westward only, as it has been fancifully supposed, or eastward, as might with equal reason have been asserted , were expanded in all directions to all the regions of the world, in which the Hindu race had settled under various denominations.

The Aryans began at Allahabad, conquered and spread out northwest, west and south, and had by YayAti’s time occupied precisely the region known as MadhyadeSa… They expanded afterwards into the Punjab and East Afghanistan, into West India and the northwest Dekhan…

Accordingly, archaeology cannot deny the possibility that Indo-Aryan and Iranian (which were preceded by Indo-Iranian) languages might have been spoken in the area of the Punjab, Pakistan/Afghanistan, southeast central Asia/northeast Iran since the second, third or even fourth millennium B.C.E. The problem is chronological. In fact, archaeologically at least, South Asian archaeologists often draw attention to a cultural continuum that can be traced as far back as Mehrgarh in the seventh millennium B.C.E. within which innovations and developments can be explained simply by internal developments and external trade. If there were no constraints stemming from the date commonly assigned to the Veda, this whole area could have included urbanites and agriculturists from the South, as well as nomads and pastoralists from the North, interacting together in the millennia B.C.E. as they always have been and still do in the present day. Both steppe dwellers and urban farmers could have been speakers of related Indo-Iranian dialects in protohistory just as they are today and have always been in recorded history. There could have been invasions, migrations, trade, cultural exchanges, all manner of interactions—cultural evolution and devolution (followed sometimes by renewed evolution)—as well as all manner of diversification in chronological time. And all within a large, heterogeneous ethnic and cultural area of people who nonetheless spoke related dialects—whether living in towns, mountains, or agricultural plains—just as has always been die history of the subcontinent.