In archaeogenetics, the term Western Steppe Herders (WSH), or Western Steppe Pastoralists, is the name given to a distinct ancestral component first identified in individuals from the Chalcolithic steppe around the start of the 5th millennium BC, subsequently detected in several genetically similar or directly related ancient populations including the Khvalynsk, Repin, Sredny Stog, and Yamnaya cultures, and found in substantial levels in contemporary populations of Europe, Central Asia, South Asia, and West Asia. This ancestry is often referred to as Yamnaya ancestry, Yamnaya-related ancestry, Steppe ancestry, or Steppe-related ancestry.
Western Steppe Herders are considered to be descended from a merger between Eastern Hunter-Gatherers (EHGs) and Caucasus Hunter-Gatherers (CHGs). The WSH component is modeled as an admixture of EHG and CHG ancestral components in roughly equal proportions, with the majority of the Y-DNA haplogroup contribution from EHG males. The Y-DNA haplogroups of Western Steppe Herder males are not uniform, with the Yamnaya culture individuals mainly belonging to R1b-Z2103 with a minority of I2a2, the earlier Khvalynsk culture also with mainly R1b but also some R1a, Q1a, J, and I2a2, and the later, high WSH ancestry Corded Ware culture individuals mainly belonging to haplogroup R1b in the earliest samples, with R1a-M417 becoming predominant over time.
Around 3,000 BC, people of the Yamnaya culture or a closely related group, who had high levels of WSH ancestry with some additional Neolithic farmer admixture, embarked on a massive expansion throughout Eurasia, which is considered to be associated with the dispersal of at least some of the Indo-European languages by most contemporary linguists, archaeologists, and geneticists. WSH ancestry from this period is often referred to as Steppe Early and Middle Bronze Age (Steppe EMBA) ancestry.
This migration is linked to the origin of both the Corded Ware culture, whose members were of about 75% WSH ancestry, and the Bell Beaker ("Eastern group"), who were around 50% WSH ancestry, though the exact relationships between these groups remains uncertain. ()
The expansion of WSHs resulted in the virtual disappearance of the Y-DNA of Early European Farmers (EEFs) from the European gene pool, significantly altering the cultural and genetic landscape of Europe. During the Bronze Age, Corded Ware people with admixture from Central Europe remigrated onto the steppe, forming the Sintashta culture and a type of WSH ancestry often referred to as Steppe Middle and Late Bronze Age (Steppe MLBA) or Sintashta-related ancestry.
The modern population of Europe can largely be modeled as a mixture of WHG (Western Hunter-Gatherers), EEF (Early European Farmers), and WSH (Western Steppe Herders), with proportions varying among different Indo-European groups such as Balts, Slavs, Germanics, and others. Contemporary Indo-Aryans of South Asia, especially upper caste populations, can largely be modeled as a mix of Bronze Age Steppe and Indus Periphery (Iranian hunter-gatherer and AASI) ancestry, with proportions varying among different communities. In contrast, non-Indo-European South Asian Dravidian populations show significant extra AASI (Ancient Ancestral South Indian) and Indus Periphery ancestry also, with relatively less Steppe contribution.
WSH ancestry peaks in Northern Europe, particularly among Irish people, Norwegians, Swedes, Belarusians, Lithuanians, Scots and Icelanders. In South Asia, WSH ancestry reaches its highest levels in the northern Indian subcontinent, especially among Kalash, Ror, Jat, Brahmin and Bhumihar. Modern-day south-central Asians, particularly the Yaghnobis and Tajiks, both Eastern Iranian peoples, exhibit strong genetic continuity with Iron Age Central Asians (Indo-Iranians). They may serve as proxies for the source of "Steppe ancestry" found among many Central Asian and Middle Eastern (or West Asian) groups, who also carry a significant BMAC (Bactria–Margiana Archaeological Complex) genetic component.
Summary
A summary of several genetic studies published in Nature and Cell during the year 2015 is given by : Western Steppe Herders component "is lower in southern Europe and higher in northern Europe", where inhabitants have roughly 50% WSH ancestry on average. (; ) It is linked to the migrations of Yamnaya populations dated to ca. 3000 BC (; ); Third-millennium Europe (and prehistoric Europe in general) was "a highly dynamic period involving large-scale population migrations and replacement" (); The Yamnaya migrations are linked to the spread of Indo-European languages (; ); The plague (Yersinia pestis) spread into Europe during the third millennium BC (), and it stemmed from migrations from the Eurasian steppes; Yamnaya peoples have the highest ever calculated genetic selection for stature ();
Nomenclature and definition 'Steppe ancestry' can be classified into at least three distinctive clusters. In its simplest and earliest form, it can be modelled as an admixture of two highly divergent ancestral components; a population related to Eastern Hunter-Gatherers (EHG) as the original inhabitants of the European steppe in the Mesolithic, and a population related to Caucasus Hunter-Gatherers (CHG) that had spread northwards from the Near East. This ancestry profile is known as 'Eneolithic Steppe' ancestry, or 'pre-Yamnaya ancestry', and is represented by ancient individuals from the Khvalynsk II and Progress 2 archaeological sites. These individuals are chronologically intermediate between EHGs and the later Yamnaya population, and harbour very variable proportions of CHG ancestry.
The later Yamnaya population can be modelled as an admixed EHG-related/CHG-related population with additional (c. 14%) Anatolian Farmer ancestry with some Western Hunter-Gatherer admixture, or alternatively can be modelled as a mixture of EHG, CHG, and Iranian Chalcolithic ancestries. This ancestry profile is not found in the earlier Eneolithic steppe or Steppe Maykop populations. In addition to individuals of the Yamnaya culture, very similar ancestry is also found in individuals of the closely related Afanasievo culture near the Altai Mountains and the Poltavka culture on the Middle Bronze Age steppe. This genetic component is known as Steppe Early to Middle Bronze Age (Steppe EMBA), or Yamnaya-related ancestry.
Expansions of Yamnaya-related populations to Eastern and Central Europe resulted in the formation of populations with admixed EMBA Steppe and Early European Farmer ancestry, such as the ancient individuals of the Corded Ware and Bell beaker cultures. In the eastern Corded Ware culture, the Fatyanovo-Balanovo group may have been the source of a back migration onto the steppe and further to the east, resulting in the formation of the Srubnaya, Sintashta, and Andronovo cultures. The genetic cluster represented by ancient individuals from these cultures is known as Steppe Middle to Late Bronze Age (Steppe MLBA) ancestry.
Origins and expansion Steppe Eneolithic
The precise location of the initial formation of so-called 'Eneolithic steppe' ancestry, which can be modeled as a relatively simple admixture of EHG and CHG-related populations, remains uncertain. Admixture between populations with Near Eastern ancestry and the EHG on the Pontic-Caspian steppe had begun by the fifth millennium BC, predating the Yamnaya culture by at least 1,000 years.
This early, 'pre-Yamnaya' ancestry was first detected in Eneolithic individuals at the Khvalynsk II cemetery and directly north of the Caucasus mountains at the Progress 2 archaeological site; this ancestry is also detected in individuals of the Steppe Maykop culture, but with additional Siberian and Native American-related admixture.
The individuals from Khvalynsk comprise a genetically heterogeneous population, with some more similar to EHGs and others closer to the later Yamnaya population. On average, these individuals can be modelled as around three-quarters EHG and one-quarter Near Eastern ("Armenian related") ancestry. These three individuals belong to Y-chromosome haplogroups R1a (which is not found in later elite Yamnaya graves), R1b, and Q1a, the first two of which are found in preceding EHG populations, which suggests continuity with the preceding EHG population.
Three individuals from the Progress 2 site in the foothills north of the Caucasus also harbour EHG and CHG related ancestry, and are genetically similar to Eneolithic individuals from Khvalynsk II but with higher levels of CHG-related ancestry that are comparable to the later Yamnaya population.
Archaeologist David Anthony speculates that the Khvalynsk/Progress-2 mating network, located between the middle Volga and the North Caucasus foothills, makes a "plausible genetic ancestor for Yamnaya".
Steppe Early to Middle Bronze Age
Early Yamnaya individuals, the Afanasievo population, and the individuals of the Poltavka and Catacomb cultures that followed the Yamnaya on the steppe comprise a genetically almost indistinguishable cluster, carrying predominantly R1b Y-DNA haplogroups with a minority of I2a.
When the first Yamnaya whole genome sequences were published in 2015, Yamnaya individuals were reported to have no Anatolian Farmer ancestry, but following larger studies it is now generally agreed that Yamnaya had around 14% Anatolian Farmer ancestry, with an additional small WHG component, which was not present in the previous Eneolithic steppe individuals.
The actual populations involved in the formation of the Yamnaya cluster remain uncertain. Proposed models have included admixture of an EHG/CHG population with European Farmers to the west (such as those of the Globular Amphorae culture or a genetically similar population), a two-way admixture of EHGs with an Iran Chalcolithic population, and a three-way admixture of EHG, CHG, and Iran Chalcolithic populations.
Lazaridis et al.(2022)conclude that Yamnaya ancestry can be modelled as a mixture of an as yet unsampled admixed EHG/CHG population with a second source from the south Caucasus, and rejects Khvalynsk Eneolithic as a source population for the Yamnaya cluster. The study also contradicts suggestions that European farmer populations of the Cucuteni-Trypillia and Globular Amphora cultures contributed ancestry to Yamnaya, because Yamnaya lack the additional hunter-gatherer ancestry found in European farmers, and carry equal proportions of Anatolian and Levantine ancestry, unlike European farmers who carry predominantly Anatolian ancestry.
Corded Ware and Bell Beaker
Genetic evidence demonstrates a major and relatively sudden population turnover in Europe during the early third millennium BC, resulting in the rapid spread of steppe ancestry along with the Corded Ware and Bell Beaker cultures.
Corded Ware individuals have been shown to be genetically distinct from preceding European Neolithic cultures of North-Central and Northeastern Europe, with around 75% of their ancestry derived from a Yamnaya-like population.
The earliest Corded Ware individuals are genetically close to Yamnaya. Admixture with local Neolithic populations resulted in later individuals genetically intermediate between Yamnaya and individuals of the Globular Amphora Culture.
A 2021 study suggests that Early Corded Ware from Bohemia can be modelled as a three way mixture of Yamnaya-like and European Neolithic-like populations, with an additional c. 5% to 15% contribution from a northeast European Eneolithic forest-steppe group (such as Pitted Ware, Latvia Middle Neolithic, Ukraine Neolithic, or a genetically similar population), a cluster the authors term 'Forest Steppe' ancestry.
In the Bell Beaker culture, high proportions (c. 50%) of steppe related ancestry are found in individuals from Germany, the Czech Republic, and Britain. The genetic turnover is most substantial in Britain, where around 90% of the gene pool was replaced within a few hundred years.