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One version of the Steppe Hypothesis of Indo-European language origins suggests that Proto-Indo European languages developed in the steppe north of the Black and Caspian seas, and that the earliest known diverging branch – Anatolian – was spread into Asia Minor by movements of steppe peoples through the Balkan peninsula during the Copper Age around 4000 BCE, as part of the same incursions from the steppe that coincided with the decline of the tell settlements.
If this were correct, then one way to detect evidence of it would be the appearance of large amounts of characteristic steppe ancestry first in the Balkan Peninsula, and then in Anatolia. However, our genetic data do not support this scenario. While we find steppe ancestry in Balkan Copper Age and Bronze Age individuals, this ancestry is sporadic across individuals in the Copper Age, and at low levels in the Bronze Age. Moreover, while Bronze Age Anatolian individuals have CHG / Iran Neolithic related ancestry, they have neither the EHG ancestry characteristic of all steppe populations sampled to date, nor the WHG ancestry that is ubiquitous in southeastern Europe in the Neolithic.
This pattern is consistent with that seen in northwestern Anatolia and later in Copper Age Anatolia, suggesting continuing migration into Anatolia from the East rather than from Europe.
An alternative hypothesis is that the ultimate homeland of Proto-Indo European languages was in the Caucasus or in Iran. In this scenario, westward movement contributed to the dispersal of Anatolian languages, and northward movement and mixture with EHG was responsible for the formation of the population associated with the Yamnaya complex. These steppe pastoralists plausibly spoke a “Late Proto-Indo European” language that is ancestral to many of the non-Anatolian branches of the Indo-European language family. On the other hand, our data could still be consistent with the Steppe-Balkans-Anatolia route hypothesis model, albeit with constraints. It remains possible that populations dating to around 1600 BCE in the regions where the Indo-European Luwian, Hittite and Palaic languages were spoken did have European hunter-gatherer ancestry. However, our results would require that such ancestry was not ubiquitous in Bronze Age Anatolia, and was perhaps tightly linked to Indo-European speaking groups. We predict that additional insight about the genetic origins of the potential speakers of early Indo-European languages will be obtained when ancient DNA data become available from additional sites in this key period in Anatolia and the Caucasus.
