Western Steppe Herders

• 1. Introduction

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  Western Steppe Herders remade the genetic landscape of Europe in a matter of centuries. In Britain alone, around ninety percent of the gene pool was replaced within a few hundred years. Researchers tracking ancient DNA gave this ancestral component several names: Yamnaya ancestry, Steppe ancestry, Western Steppe Pastoralists. All these labels describe the same underlying population, one whose origins lay in a mixing zone between two genetically distant ancient peoples on the Eurasian steppe. The questions this story raises are large. Who were these people before they became a force on the landscape? What did they look like? And whose bodies, across Europe, South Asia, and Central Asia, still carry their genes today?

• 2. The First Mixture

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  Admixture between Near Eastern-related populations and Eastern Hunter-Gatherers on the Pontic-Caspian steppe had begun by the fifth millennium BC. This was at least 1,000 years before the Yamnaya culture appeared.

  The earliest clear evidence comes from two sites. One is the Khvalynsk II cemetery; the other is Progress 2, a location in the foothills directly north of the Caucasus mountains. Individuals from Khvalynsk II were not genetically uniform. Some were close to Eastern Hunter-Gatherers; others resembled the later Yamnaya population much more closely. The group as a whole can be modeled as roughly three-quarters Eastern Hunter-Gatherer and one-quarter Near Eastern ancestry. Three individuals from Progress 2 shared a similar profile, but with higher Caucasus Hunter-Gatherer levels, approaching what the Yamnaya would later show. David Anthony, an American archaeologist, has described the Khvalynsk-Progress 2 mating network as a plausible genetic ancestor for the Yamnaya. That network, he notes, was located between the middle Volga and the North Caucasus foothills. Anthony also notes that the Sredny Stog culture, which preceded the Yamnaya on the same steppe, had mostly WSH ancestry with slight EEF admixture. The Khvalynsk culture, further east, was purely WSH.

  The Khvalynsk individuals belonged to Y-chromosome haplogroups R1a, R1b, and Q1a. The first two appear in preceding Eastern Hunter-Gatherer populations too, pointing to paternal continuity from that line. No Caucasus Hunter-Gatherer Y-DNA appears among the Yamnaya. Anthony concludes this means the admixture occurred between EHG and WHG males on one side, and CHG and EEF females on the other. This reasoning also rules out the Maikop culture as a significant contributor to WSH ancestry or culture. Anthony places the original EHG-CHG admixture on the eastern Pontic-Caspian steppe at around 5,000 BC. EEF admixture arrived later, in the steppe's southern regions. He also concludes that Indo-European languages began as a dominant tongue spoken by Eastern Hunter-Gatherers. Over time, contact with Caucasus Hunter-Gatherer speakers introduced elements into its phonology, morphology, and lexicon.

  When whole genome sequences of Yamnaya individuals were first published in 2015, analysts found no Anatolian Farmer ancestry. Later and larger studies revised that finding. Yamnaya did carry around 14% Anatolian Farmer ancestry, along with a small Western Hunter-Gatherer component. The exact source of that Anatolian Farmer ancestry remains unresolved. A 2022 study by Lazaridis and colleagues modeled Yamnaya as a mixture of an as-yet-unsampled EHG-CHG population with a second source from the south Caucasus. The same study rejected Khvalynsk Eneolithic as a direct source population for the Yamnaya cluster.

• 3. Across Eurasia

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  Around 3,000 BC, people of the Yamnaya culture set out on a massive expansion across Eurasia. Most contemporary linguists, archaeologists, and geneticists link this movement to the dispersal of at least some of the Indo-European languages.

  Members of the Corded Ware culture, which spread across northern and central Europe, derived around 75% of their ancestry from a Yamnaya-like population. The earliest Corded Ware individuals are genetically close to Yamnaya. Admixture with local Neolithic populations produced later Corded Ware individuals who were intermediate between Yamnaya and populations like the Globular Amphora Culture. A 2021 study found that Early Corded Ware from Bohemia can be modeled as a three-way mixture. The components are a Yamnaya-like population, a European Neolithic-like population, and a northeast European Eneolithic forest-steppe group. The authors called this third element 'Forest Steppe' ancestry, estimating its contribution at between 5% and 15%.

  Bell Beaker populations from Germany, the Czech Republic, and Britain carried around 50% steppe-related ancestry. The earliest Bell Beaker individuals from Bohemia with steppe ancestry are genetically similar to Corded Ware individuals, which suggests continuity between the two. Later Bell Beaker individuals added around 20% Middle Eneolithic ancestry.

  Across Europe, this expansion replaced EEF paternal lineages almost entirely with EHG-derived types, mainly R1b and R1a. EEF mitochondrial lineages remained frequent. Anthony notes this asymmetry, suggesting that WSH males mixed with EEF females rather than migrating in balanced family groups.

  During the Bronze Age, the Fatyanovo group within the eastern Corded Ware culture appears to have migrated back onto the steppe. This back-migration gave rise to the Sintashta culture in the southern Urals. Related cultures formed further east: the Andronovo in Central Asia and the Srubnaya on the Pontic-Caspian steppe. All three carry substantial Yamnaya-related ancestry combined with European Farmer admixture. This genetic cluster is known as Steppe Middle to Late Bronze Age ancestry, or Steppe MLBA. Narasimhan and colleagues, writing in 2019, identified Steppe MLBA ancestry as likely the main vector for this southward spread. They dated the movement into South Asia to the early 2nd millennium BC.

  Among Yamnaya individuals, Y-DNA was predominantly R1b-Z2103, with a minority of I2a2. In the Corded Ware culture that emerged from their expansion, R1a-M417 became predominant over time.

• 4. Bodies and Biology

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  Osteological evidence shows the average Yamnaya male stood 175.5 cm tall, with long-headed, or dolichocephalic, crania. The Catacomb culture people who followed them on the steppe were stockier and had more rounded, or brachycephalic, crania. A 2024 study argued that differences in Yamnaya-like ancestry between Northern and Southern Europeans account for the observable height difference between those populations today.

  Early Bronze Age Yamnaya are believed to have had mostly intermediate complexions, brown eyes, and dark hair. Lazaridis and colleagues in 2022 addressed this directly. Even in later Bronze Age steppe populations, the composite phenotype of blond hair, blue eyes, and pale skin was extremely rare in any single individual. Corded Ware people had a higher proportion of blue eyes, most likely through admixture with Western Hunter-Gatherers, who were predominantly blue-eyed. As WSHs interacted with Early European Farmers, who fixed the derived SLC24A5 allele for lighter skin during the Anatolian Neolithic, phenotypes began to shift. By the Sintashta Middle to Late Bronze Age populations, blond hair frequencies reached around 38.5%, blue eyes around 30.8%, and pale skin around 7.7%. Lazaridis and colleagues note that 'intermediate' complexion in early WSH peoples corresponds to complexions seen today in Mediterranean populations. Northern European paleness developed through continuous selection pressure long after the initial WSH expansion.

  The rs12821256 allele of the KITLG gene is associated with blond hair and melanocyte development. It first appears in an Ancient North Eurasian individual from Siberia dated to around 15,000 BC. It later shows up in three Eastern Hunter-Gatherers from Samara, Motala, and Ukraine, and in subsequent individuals with WSH ancestry. Geneticist David Reich concludes that the migration of Ancient North Eurasian-related people most likely brought this allele to Europe. Today it exists in hundreds of millions of copies in modern European populations.

  Steppe-derived populations, including the Yamnaya, are thought to have brought lactose tolerance into adulthood to Europe from the Eurasian steppe. Five ancient DNA samples from Yamnaya sites showed a frequency of over 25% for the associated allele. The hypothesis is that this ability gave steppe migrants a biological advantage over European populations who lacked it. Eurasian Steppe populations carry this allele at higher frequencies than European farmers and hunter-gatherers who had no steppe admixture.

  When researchers examined West Eurasia as a whole, they found that inhabitants of the Southern Arc had darker average pigmentation than those further north. Light phenotypes appeared in both regions at similar early dates and grew in parallel across subsequent millennia, driven by selection pressure in both areas.

• 5. Who Carries It Today

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  WSH ancestry peaks in Northern Europe, reaching its highest concentrations among Irish, Norwegian, Swedish, Belarusian, Lithuanian, Scottish, and Icelandic populations. In South Asia, it is highest in the northern subcontinent, especially among Brahmin, Bhumihar, Ror, Jat, and Kalash communities. Contemporary Indo-Aryans of South Asia can largely be modeled as a mixture of Bronze Age Steppe ancestry and Indus Periphery ancestry. The Indus Periphery component itself combines Iranian hunter-gatherer and Ancient Ancestral South Indian ancestry. Proportions of steppe ancestry vary considerably between communities.

  Non-Indo-European Dravidian-speaking populations show a different genetic profile. They carry significant additional Ancient Ancestral South Indian and Indus Periphery ancestry, with relatively less steppe contribution. Research by Pathak and colleagues in 2018 addressed this distinction. Dravidian people and Indo-Europeans of the Gangetic Plains showed Yamnaya ancestry but no Steppe MLBA ancestry. Northwestern Indian and Pakistani populations showed both types.

  Modern Europeans can largely be modeled as a mixture of three ancestral components: Western Hunter-Gatherers, Early European Farmers, and Western Steppe Herders. Proportions vary across Indo-European-speaking groups, from Balts and Slavs to Germanics and others. Inhabitants of Northern Europe have roughly 50% WSH ancestry on average, while southern European populations have lower levels.

  The Yaghnobis and Tajiks, both Eastern Iranian peoples, show strong genetic continuity with Iron Age Central Asians. Researchers have proposed they may serve as proxies for the steppe ancestry source found among many Central Asian and West Asian groups. Those populations also carry a significant component from the Bactria-Margiana Archaeological Complex, or BMAC, an ancient culture whose genetic contribution remains detectable today.

  A 2015 summary of genetic studies added one further dimension to this picture. The plague pathogen Yersinia pestis entered Europe during the third millennium BC, stemming from migrations out of the Eurasian steppes. It traveled alongside the same ancestry that still marks populations from Ireland to the northern Indian subcontinent.