We can directly go into the topic. So as per Narasimhan there is some Iranian ancestry in Yamnaya.
Here is the opinion of David Reich about the PIE homeland from his book
“While the genetic findings point to a central role for the Yamnaya in spreading Indo-European languages…those findings do not yet resolve the question of the homeland of the original Indo-European languages…Anatolian langauges…did not share the full wagon and wheel vocabulary present in all Indo-European languages spoken today. Ancient DNA available from this time in Anatolia shows no evidence of steppe ancestry similar to that in the Yamnaya…This suggests to me that the most likely location of the population that first spoke an Indo-European language was south of the Caucasus Mountains, perhaps in present-day Iran or Armenia, because ancient DNA from people who lived there matches what we would expect for a source population both for the Yamnaya and for ancient Anatolians.”
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From a paper which is co authored by Reich
“To the north, a population related to people of the Iran Chalcolithic contributed ~43% of the ancestry of early Bronze Age populations of the steppe. The spread of Near Eastern ancestry into the Eurasian steppe was previously inferred without access to ancient samples, by hypothesizing a population related to present-day Armenians as a source”
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It maybe noted that all ancient Iranian samples, later than 6000 BC, as per the recent Narasimhan et al paper, have substantial levels of Anatolian Farmer ancestry. So as per Reich, a mixed population of largely Iranian & Anatolian Farmer ancestry is the likely source of the spread of Indo-European languages into the steppe. Further, in the very same 2016 paper, the ancient Anatolian Chalcolithic samples could also be modeled as having nearly half of their ancestry from Iran Chalcolithic. Thus, as per Reich, the Iranian Chalcolithic, that can be shown as a suitable admixture source for both Chalcolithic & Bronze Age Anatolians (where in LBA the IE Anatolian languages were spoken) as well as the Yamnaya on the steppe, is the most likely original source of PIE ancestry.
“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”
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“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”
Page 13
“In Anatolia, Bronze Age samples, including from Hittite speaking settlements associated with the first written evidence of IE languages, show genetic continuity with preceding Anatolian Copper Age (CA) samples and have substantial Caucasian hunter-gatherer (CHG)–related ancestry but no evidence of direct steppe admixture.”
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Therefore the majority opinion among geneticists at the moment seems to be that the PIE homeland is likely either Armenia or Iran based on the evidence that CHG/Iran Chalcolithic populations serve as ideal source populations for both the Yamnaya pastoralists of the steppe as well as the Bronze Age Anatolians.
Another paper by Wang et al which for the first time published large no of ancient samples from Chalcolithic Caucasus including the much awaited samples from populations of the Maykop culture which is traditionally considered to have strongly influenced the formation of the Yamnaya culture on the steppe.
A few pertinent observations from this study :-
The Eneolithic steppe populations also existed in the North Caucasus Piedmont Steppe at sites such as Progress & Vonyuchka but had a slightly different ancestry profile to that of Eneolithic steppe populations from Samara & Khwalynsk. The Eneolithic Steppe populations could be modelled as admixture of nearly equal amounts of EHG and CHG components.
Similarly, we find Steppe Maykop samples from the steppe preceding the Yamnaya by a few centuries, which also show CHG ancestry but no Anatolian Farmer ancestry. The Steppe Maykop, in addition, also show an excess of East Eurasian and ANE ancestry.
What also emerges very clearly from Wang et al is the fact that the CHG/Iran N type ancestry on the steppe emerged without any admixed Anatolian Farmer ancestry as can be observed in the Eneolithic Steppe and Steppe Maykop samples who show CHG/Iran N admixture but no Anatolian Farmer admixture.
“An important observation is that Eneolithic Samara and Eneolithic steppe individuals directly north of the Caucasus had initially not received AF gene flow. Instead, the Eneolithic steppe ancestry profile shows an even mixture of EHG- and CHG ancestry, suggesting an effective cultural and genetic border between the contemporaneous Eneolithic populations, notably Steppe and Caucasus. Due to the temporal limitations of our dataset, we currently cannot determine whether this ancestry is stemming from an existing natural genetic gradient running from EHG far to the north to CHG/Iran in the south or whether this is the result of Iranian/CHG-related ancestry reaching the steppe zone independently and prior to a stream of AF ancestry, where they mixed with local hunter-gatherers that carried only EHG ancestry.”
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The fact that, as we noted earlier, the Iranian populations from Iran Proper post-6000 BC and even North Caucasus populations around 4500 BC , as evidenced by Wang et al itself, had substantial Anatolian Farmer admixture effectively rules out the admixture coming from the south via the Caucasus route.
Wang et al suggest that even during the transition from Eneolithic to the Yamnaya phase, the Anatolian Farmer (AF) ancestry might not have come to the steppe via the Caucasus but largely if not solely through the European Farmer populations adjacent to the steppe on its west.
“All later steppe groups, starting with Yamnaya, deviate from the EHG-CHG admixture cline towards European populations in the West. We show that these individuals had received AF
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ancestry, in line with published evidence from Yamnaya individuals from Ukraine (Ozera) and Bulgaria. In the North Caucasus, this genetic contribution could have occurred through immediate contact with Caucasus groups or further south. An
alternative source, explaining the increase in WHG-related ancestry, would be contact with contemporaneous Chalcolithic/EBA farming groups at the western periphery of the Yamnaya distribution area, such as Globular Amphora and Cucuteni–Trypillia from Ukraine, which have been shown to carry AF ancestry”
Even the Iranian related ancestry is found in western Mediterranean islands during bronze age. In a paper released in nature
“A series of studies have documented how Steppe pastoralist-related ancestry reached central Europe by at least 2500 BCE, while Iranian farmer-related ancestry was present in Aegean Europe by at least 1900 BCE.”
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In the new genetic studies chinthalapati et al 2022
“The second major migration occurred when populations associated with the Yamnaya culture in the Pontic-Caspian steppe expanded to central and western Europe from far eastern Europe. Our analysis reveals the precise timing of the genetic formation of these early Steppe pastoralists groups–Yamnaya and Afanasievo–occurred ~4,400-4,000 BCE. This estimate predates the archaeological evidence by more than a millennium and suggests the presence of an ancient “ghost” population of proto-Yamnaya around this time. Understanding the source and location of this ghost population will provide deep insights into the history of Pontic-Caspiancultures and the origin of Indo-European languages that have been associated to have spread with Steppe pastoralists ancestry to Europe and South Asia”
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There was a similar ghost population reference in Narasimhan et al 2019, which I have quoted in previous post.
So by all the evidences it is clear that the steppe eneolithic population is equal mixture of EHG(Eastern European Hunter Gathers) and CHG/Iranian ancestry. Also Reich also point outs that to the south of Caucasus the Ancient Armenians and Iranians may have spoken Indo European languages prior to steppe. So the location which have this Iranian related ancestry is the Proto Indo European homeland. The areas in which the ancestry existed prior to steppe is south of Caucasus (Armenia, Iran) or to the east, central Asia or South Asia. (Note early steppe eneolithic population has no Anatolian admixture. so there is greater chance that central Asia or South Asia as PIE homeland).
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