Caucasian Hunter-Gatherer (CHG) was dubbed by a genetic study in 2015 of several modern European, Caucasian and Near Eastern populations. A previously unidentified lineage, CHG ancestry was represented by a Upper Palaeolithic specimen from Satsurblia cave (ca. 11000 BC), and a Mesolithic one from Kotias Klde cave, in western Georgia (ca. 6000 BC).
The Caucasus hunter-gatherers descended from a population that split off very early around 45,000 years ago, pre-dating the split that led to differentiated populations that descended separately to Ust'-Ishim man, Oase1 and European hunter-gatherers. The Caucasus hunter-gatherers managed to survive in isolation through the last Ice Age as a distinct population.
The 2015 study by Fu et al. analysed "Eurasian steppe ancestry" – which is associated with the so-called Ancient North Eurasian lineage – among modern European populations, which is linked to the Indo-European expansion. In comparison to modern human populations, the Satsurblia individual is closest to modern populations from the South Caucasus.
The study detected a split between CHG and so-called "Western European Hunter-Gatherer" (WHG) lineages, about 45,000 years ago, the presumed time of the original peopling of Europe. CHG separated from the "Early Anatolian Farmers" (EAF) lineage later, at 25,000 years ago, during the Last Glacial Maximum. (CHG was extrapolated from, among other sources, the genomes of two fossils from western Georgia – one about 13,300 years old (Late Upper Paleolithic) and the other 9,700 years (Mesolithic), which were compared to the 13,700 year-old Bichon man genome (found in Switzerland).
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. The researchers found that these Caucasus hunters were probably the source of the Near Eastern DNA in the Yamnaya. 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.
Yardumian et al. (2017) in a population genetics study on the Svans of northwestern Georgia found significant heterogenity in mt-DNA, with common haplogroups including U1‐U7, H, K, and W6, while Y-DNA haplogroups were less diverse, 78% of Svan males being bearers of Y-haplogroup G2a. Wang et al (2018) 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 Lazaridis et al. (2016), "a population related to the people of the Iran Chalcolithic contributed ~ 43 % of the ancestry of early Bronze Age populations of the steppe." These Iranian Chacolithic people were a mixture of "the Neolithic people of western Iran, the Levant, and Caucasus Hunter Gatherers".[note 1] The Near East population were most likely hunter-gatherers from the Caucasus (CHG), though one study suggested that farmers dated to the Chalcolithic era from what is now Iran may be a better fit for the Yamanya's Near Eastern descent.
Lazaridis et al. (2016) proposes a different people, likely from Iran, as the source for the Middle Eastern ancestry of the Yamnaya people, finding that "a population related to the people of the Iran Chalcolithic contributed ~43% of the ancestry of early Bronze Age populations of the steppe". That study asserts that these Iranian Chalcolithic people were a mixture of "the Neolithic people of western Iran, the Levant, and Caucasus Hunter Gatherers". However, a different analysis, carried out by Gallego-Llorente et al. (2016), concludes that Iranian populations are not a likelier source of the 'southern' component in the Yamnaya than Caucasus hunter-gatherers.
The CHG lineage was found to have contributed significantly to the Yamnaya lineage of Chalcolithic pastoralists in the Pontic steppe, which in turn expanded into Europe from about 5,000 years ago (Indo-European expansion). CHG admixture was also found in South Asia, in a possible marker of the Indo-Aryan migration there.
The proto-Indo-Europeans, i. E. the Yamnaya people and the related cultures, seem to have been a mix from eastern European hunter-gatherers; and people related to the near east, such as Caucasus hunter-gatherers and Iran Chalcolithic people, with a Caucasian hunter-gatherer component.[note 2]  Each of those two populations contributed about half the Yamnaya DNA. According to co-author Andrea Manica of the University of Cambridge:
The question of where the Yamnaya come from has been something of a mystery up to now ... we can now answer that, as we've found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation.
According to Jones et al. (2015), Caucasus hunter-gatherers (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 marking the arrival of Indo-Aryan languages."[note 3]
There was probably a migration of populations from the Near East and Caucasus to Europe during the Mesolithic, around 14,000 years ago, much earlier than the migrations associated with the Neolithic Revolution. A few specimens from the Villabruna Cluster also show genetic affinities for East Asians that are derived from gene flow. The light skin pigmentation characteristic of modern Europeans is estimated to have spread across Europe in a "selective sweep" during the Mesolithic (19,000 to 11,000 years ago). The associated TYRP1 alleles, SLC24A5 and SLC45A2, emerge around 19,000 years ago – during the LGM and most likely in the Caucasus. The HERC2 variation for blue eyes first appears around 13,000 to 14,000 years ago in Italy and the Caucasus.
Caucasus Hunter Gatherers coexisted with the formation of the Yamna culture, since Samara hunter-gatherers featured only Eastern European Hunter Gatherer (EHG) ancestry and no CHG ancestry, whereas Yamna samples had up to 43% of CHG ancestry.
Margaryan et al. (2017) analysing South Caucasian ancient mitochondrial DNA found continuity in descent in the maternal line for 8,000 years. The same study also found a rapid increase of the population at the end of the Last Glacial Maximum, about 18,000 years ago. Modern Armenians were found to derive from an admixture event in the Bronze Age (3rd to 2nd millennia BCE), which combined various Eurasian lineages. Since the time of the Bronze Age collapse, about 1200 BCE, Armenians have remained genetically isolated as a population, with a higher genetic affinity to Neolithic Anatolians, the Neolithic Levant, and Neolithic European farmers than to modern Near Eastern populations.
- Prehistoric Georgia
- Prehistoric Armenia
- Prehistoric Azerbaijan
- Peoples of the Caucasus
- Proto-Northwest Caucasian language
- Indo-European migrations
- Ancient Near East
- Y-DNA haplogroups in populations of the Near East
- Fu, Qiaomei; Posth, Cosimo (May 2, 2016). "The genetic history of Ice Age Europe". Nature. doi:10.1038/nature17993.
- "Europe's fourth ancestral 'tribe' uncovered". BBC. 16 November 2015.
- Dutchen, Stephanie (May 2, 2016). "History on Ice". Harvard Medical School. Retrieved 11 May 2016.
- Fu 2016.
- Jone 2015.
- A. Yardumian et al. (2017), "Genetic diversity in Svaneti and its implications for the human settlement of the Highland Caucasus", Am J Phys Anth 164(4), December 2017, doi:10.1002/ajpa.23324.
- C. Wang et al., "The genetic prehistory of the Greater Caucasus", May 16, 2018, doi: https://doi.org/10.1101/322347
- Lazaridis 2016, p. 8.
- Jones et al. 2015.
- Lazaridis et al. 2016, p. 8.
- Lazaridis; et al. "The genetic structure of the world's first farmers". eurogenes.blogspot. (pre-print).
- Lazaridis; et al. "The genetic structure of the world's first farmers". anthrogenica.com.
- Gallego-Llorente, M.; Connell, S.; Jones, E. R.; Merrett, D. C.; Jeon, Y.; Eriksson, A.; et al. (2016). "The genetics of an early Neolithic pastoralist from the Zagros, Iran". Scientific Reports. Bibcode:2016NatSR...631326G. doi:10.1038/srep31326.
- Jones, E. R. et al., "Upper Palaeolithic genomes reveal deep roots of modern Eurasians". Nat. Commun. 6:8912 doi: 10.1038/ncomms9912 (2015).
- Haak 2015, p. 3.
- Jones 2015.
- Eurogenes.blogspot, The genetic structure of the world's first farmers (Lazaridis et al. preprint)
- Mathieson 2015.
- S. Beleza et al., "The Timing of Pigmentation Lightening in Europeans", Molecular Biology and Evolution, Volume 30, Issue 1, 1 January 2013, Pages 24–35, doi:10.1093/molbev/mss207. see also: E. R. Jones, "Upper Palaeolithic genomes reveal deep roots of modern Eurasians", Nature Communications volume 6, Article number: 8912 (2015), https://www.nature.com/articles/ncomms9912 doi:10.1038/ncomms9912].
- Anthony, D. 2007. The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World. Princeton and Oxford: Princeton University Press.
- Margaryan and Derenko et al.: "Eight Millennia of Matrilineal Genetic Continuity in the South Caucasus" http://www.cell.com/current-biology/fulltext/S0960-9822(17)30695-4 , DOI: 10.1016/j.cub.2017.05.087
- M. Haber et al., "Genetic evidence for an origin of the Armenians from Bronze Age mixing of multiple populations", European Journal of Human Genetics 24 (2015), 931–936 (2016), doi:10.1038/ejhg.2015.206.
- See also:
- eurogenes.blogspot, The genetic structure of the world's first farmers (Lazaridis et al. preprint)
- For what they were... we are (2016) Ancient genomes from Neolithic West Asia
- Lazaridis et al. (2016), referring to Haak et al. (2015): "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."
Eurogenes Blog: "Lazaridis et al. show that Early to Middle Bronze Age steppe groups, including Yamnaya, tagged by them as Steppe EMBA, are best modeled with formal statistics as a mixture of Eastern European Hunter-Gatherers (EHG) and Chalcolithic farmers from western Iran. The mixture ratios are 56.8/43.2, respectively. However, they add that a model of Steppe EMBA as a three-way mixture between EHG, the Chalcolithic farmers and Caucasus Hunter-Gatherers (CHG) is also a good fit and plausible."
- Stephanie Dutchen (2014), New Branch Added to European Family Tree. Genetic analysis reveals Europeans descended from at least three ancient groups;
- Eppie Jones (2015), Europe's fourth ancestral 'tribe' uncovered;
- Dieneke's Anthropology Blog, West Asian in the flesh (hunter-gatherers from Georgia) (Jones et al. 2015);
- For what they were… we are (2016), Caucasus and Swiss hunter-gatherer genomes.
- Jones et al. (2015) further note that "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."