Caucasus hunter-gatherer (CHG), also called Satsurblia cluster, is an anatomically modern human genetic lineage, first identified in a 2015 study, based on the population genetics of several modern Western Eurasian (European, Caucasian and Near Eastern) populations.
It represents an ancestry maximised in some Upper Paleolithic and Mesolithic hunter-gatherer groups in the Caucasus. These groups are also very closely related to Mesolithic hunter-gatherers and Neolithic farmers and pastoralists in the Iranian Plateau (Iranian hunter-gatherer cluster), who are sometimes included within the CHG group.
Ancestry that is closely related to CHG-Iranian hunter gatherers and farmers is also known from further east, including from the Bactria–Margiana Archaeological Complex and the Harappan/Indus Valley Civilisation. Caucasus hunter-gatherers and Eastern hunter-gatherers are ancestral in roughly equal proportions to the Western Steppe Herders (WSH), who were widely spread across Europe and Asia beginning during the Chalcolithic.
Formation and development The CHG lineage is suggested to have separated from the ancestor of western hunter-gatherers (WHGs) probably during the Last Glacial Maximum (LGM, sometime between 45,000 and 26,000 years ago). They later separated from the Anatolian hunter-gatherers (AHG), suggested to around 25,000 years ago during the late LGM.
The CHG survived in isolation as a distinct population since the late LGM period, and display high genetic affinities to Mesolithic and Neolithic populations on the Iranian plateau, such as Neolithic specimens found in Ganj Dareh. The CHG have higher genetic affinities to European and Anatolian groups than do Iranian hunter-gatherers, suggesting a possible cline and geneflow into the CHG and less into Mesolithic and Neolithic Iranian groups.
One model inferred that the Mesolithic/Neolithic Iranian lineage basal to the CHG derive significant amounts of their ancestry from basal Eurasian (), and the remaining ancestry () is closer to ancient north Eurasians (ANE) or eastern European hunter-gatherer (EHG). The CHG had an additional ANE-like component () compared to Neolithic Iranians, suggesting they may have had continuous contact with Eastern Hunter-Gatherers to their north.
The CHG also carry around 20% additional Paleolithic Caucasus/Anatolian ancestry. Lazaridis et al. (2016) models the CHG as a mixture of Neolithic Iranians, western hunter-gatherers and Eastern Hunter-Gatherers. CHG cluster with early Iranian farmers, who do not share alleles with early Levantine farmers.
An alternative model by Vallini et al. (2024) with little ANE ancestry suggests that the initial Iranian hunter-gatherer-like population which is basal to the CHG formed primarily from a deep Ancient West Eurasian lineage ('WEC2', ), and from varying degrees of ancient east Eurasian () and Basal Eurasian () components. The Ancient West Eurasian component associated with Iranian hunter-gatherers (WEC2) is inferred to have diverged from the West Eurasian Core lineage (represented by Kostenki-14; WEC), with the WEC2 component staying close to the Iranian Plateau, while the proper WEC component expanded into Europe.
Irving-Pease et al. (2024) models CHG as being derived from an Out of Africa population that split into basal Northern Europeans and West Asians. The latter was where CHG originated from.
At the beginning of the Neolithic, at , CHG were probably distributed across western Iran and the Caucasus, and similar people arrived before 6000 BC in Pakistan and north-west India. A roughly equal merger of CHG and eastern hunter-Gatherers on the Pontic–Caspian steppe created the Western Steppe Herders (WSHs). The WSHs formed the Yamnaya culture and expanded greatly throughout Europe during the Late Neolithic and Early Bronze Age .
Caucasus hunter gatherer/Iranian-like ancestry, was first reported as maximized in hunter-gatherers from the South Caucasus and early herders/farmers in northwestern Iran, particularly the Zagros, hence the label "CHG/Iranian".
Further research
Jones et al. (2015) analyzed genomes from males from western Georgia, in the Caucasus, from the Late Upper Palaeolithic (13,300 years old) and the Mesolithic (9,700 years old). These two males carried Y-DNA haplogroup: J* and J2a, later refined to J1-FT34521, and J2-Y12379*, and mitochondrial haplogroups of K3 and H13c, respectively. Their genomes showed that a continued mixture of the Caucasians with Middle Eastern populations took place up to 25,000 years ago, when the coldest period in the last Ice Age started.
CHG ancestry was also found in an Upper Palaeolithic specimen from Satsurblia cave (dated ), and in a Mesolithic one from Kotias Klde cave, in western Georgia (dated ). The Satsurblia individual is closest to modern populations from the South Caucasus.
Margaryan et al. (2017) analysing South Caucasian ancient mitochondrial DNA found a rapid increase of the population at the end of the Last Glacial Maximum, about 18,000 years ago. The same study also found continuity in descent in the maternal line for 8,000 years.
According to Narasimhan et al. (2019) Iranian farmer related people arrived before 6000 BCE in Pakistan and north-west India, before the advent of farming in northern India. They suggest the possibility that this "Iranian farmer–related ancestry [...] was [also] characteristic of northern Caucasus and Iranian plateau hunter-gatherers."
According to Ghalichi et al. (2024), find that the Anatolia Neolithic to CHG-Iran_N cline formed around 6300–6000 BC, consistent with previous estimates, and the EHG–CHG cline formed around 5800–5300 BC. Interaction between Anatolia and the Caucasus increased during the Chalcolithic and the Bronze Ages, leading to the spread of CHG ancestry. It also diffused into the Mediterranean, an early indication of which is found in Anatolian farmer groups from Tepecik-Çiftlik.
Among modern populations, CHG ancestry peaks in indigenous Caucasian populations, as well as in populations that live in the east of the Caucasus, Iran and South Asia. However, high affinities between CHG and South Asians probably reflect affinities to both CHG and Iranian Neolithic individuals.
Caucasus Hunter Gatherers had light and intermediate skin tones and brown eyes.
Proto-Indo Europeans
During the Neolithic and early Eneolithic, likely during the 4th millennium BC, Caucasus hunter-gatherers (CHGs) mixed with Eastern Hunter-gatherers (EHGs) on the Pontic–Caspian steppe, with the resulting population, almost half-EHG and half-CHG, forming the genetic cluster known as Western Steppe Herder (WSH). According to David W. Anthony, Caucasus hunter-gatherer ancestry of Yamnaya is often with higher than 50%. As well as an overwhelming WSH ancestry, Yamnaya also have additional admixture from Anatolian and Levantine farmers, and the Western Hunter-gatherers (WHGs).
According to co-author Andrea Manica of the University of Cambridge:
Some scholars argue that the archaic PIE ('Indo-Anatolian') language may have originated among a CHG-rich population in Western Asia, based on the lack of EHG ancestry in the probable speakers of Anatolian languages. Others, such as Anthony, suggest that PIE was spoken by EHGs living in Eastern Europe.
According to Jones et al. (2015), Caucasus hunter-gatherer (CHG) "genomes significantly contributed to the Yamnaya steppe herders who migrated into Europe ~3,000 BCE, supporting a formative Caucasus influence on this important Early Bronze Age culture. CHG left their imprint on modern populations from the Caucasus and also Central and South Asia possibly correlating with the arrival of Indo-Aryan languages.": "Caucasus hunter-gatherers (CHG) belong to a distinct ancient clade that split from western hunter-gatherers ~45 kya, shortly after the expansion of anatomically modern humans into Europe and from the ancestors of Neolithic farmers ~25 kya, around the Last Glacial Maximum." For example, about 50–70% of Armenian ancestry is derived from CHG, persisting from Neolithic times to the present.
Wang et al. (2019) analysed genetic data of the North Caucasus of fossils dated between the 4th and 1st millennia BC and found correlation with modern groups of the South Caucasus, concluding that "unlike today – the Caucasus acted as a bridge rather than an insurmountable barrier to human movement".
According to Allentoft et al. (2024), The arrival and admixture of CHG with Caspian steppe cultures is dated to about 7,300-years-old, which is seen in two ancient samples from Golubaya Krinitsa with 18–24% admixture. suggestive of CHG-related ancestry extending past the middle Don to the Azov Sea coast and the Dnipro Valley during the second half of the 6th millennium BCE.
A 7000-year-old genome from the Caucasus (Nalchik) links the Volga's first herders to farmers of W. Asia and it seems that in the first half of the 5th millennium BCE cultural and mating networks helped agriculture and pastoralism spread from West Asia across the Caucasian, into the steppes between the Don and the Volga in Eastern Europe.
Ancient Greece, Aegean and Italy Beyond contributing to the population of mainland Europe through Bronze Age pastoralists of the Yamnaya, CHG also appears to have arrived on its own in the Aegean without Eastern European hunter–gatherer (EHG) ancestry and provided approximately 9–32% of ancestry to the Minoans. The origin of this CHG component might have been Central Anatolia.
Genetic analysis shows that Iranian-related ancestry, which was widespread in the Aegean by the Middle Bronze Age in association with the Minoan and Mycenaean cultures, had also spread as far west as Sicily in substantial proportion at least by the time of the Mycenaeans. One possibility is this ancestry spread west along with the Mycenaean cultural expansion. An arrival of the CHG-related component in Southern Italy from the Southern part of the Balkan Peninsula, including the Peloponnese, is compatible with the identification of genetic corridors linking the two regions and the presence of Southern European ancient signatures in Italy. Collected data from Iron Age individuals dating from 900 to 200 BCE (including the Republican period) group shows a clear ancestry shift from the Copper Age, interpreted by ADMIXTURE as the addition of a Steppe-related ancestry component, and an increase in the Neolithic-Iranian component.
Iran/Caucasus-related genetic influx was inferred in published individuals from the later Neolithic phases on the mainland (Peloponnese, around the fifth millennium BC) —but not earlier— as well as most of the EBA individuals from Euboea, Aegina and Koufonisia. comparison between ancient and modern samples, showing an overall similarity between Southern Italian and Iron Age Individuals, may suggest that the CHG/Iran_Neolithic signature reached the East side of the Adriatic Sea multiple times, or possibly as a continuous gene flow. Also in the Rocavecchia (1500–1365 BCE) In southern Italy.
In prehistoric Sardinia, the component associated with Iranian farmers, or Caucasus-related ancestry, present in Mainland Italy since the Neolithic (together with the EEF and WHG components), gradually increases from 0% in the Early Chalcolithic to about 5.8% in the Bronze Age. In Novilara, Iron age, PN43 is slightly shifted towards Near Eastern populations in the PCA and shows a high proportion of the CHG/Iran Neolithic component in Admixture analysis. they confirmed these results also with Admixture analysis, where a great genetic influence from the CHG/Iran Neolithic component is observed in all Late Antiquity Pesaro individuals.