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Post by Admin on Nov 3, 2024 18:34:15 GMT
The Caucasus region and surrounding areas lie at the interface of Europe and Asia. By the mid-Holocene, the Greater Caucasus Mountain range functioned as a semipermeable barrier through which ideas, technologies, languages and people moved1. The wide variety of climate zones in the topographically complex South Caucasus supported a high level of biodiversity, whereas the mountain highlands and hilly piedmont zones in the North Caucasus transitioned into the flat open grasslands of the West Eurasian steppe belt9. With its diverse ecologies and rich metal resources, the Caucasus region became a crucible of the Bronze Age (BA) and the birthplace of the earliest steppe pastoralist societies during the fourth millennium BC (ref. 2). The subsequent continental expansions of these steppe pastoralist groups over the next two millennia ultimately reshaped the genetic make-up, languages and cultural trajectories of much of Eurasia10,11. However, their emergence out of local hunter-gatherer groups and connections to nascent farming communities in the Fertile Crescent remain poorly understood, as does their ultimate disappearance in the second millennium BC.
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Post by Admin on Nov 5, 2024 19:59:49 GMT
Genetic structure We report new genome-wide data for 131 individuals from 38 archaeological sites and 84 new radiocarbon dates across and around the Caucasus region, including the piedmont and steppe zones, tripling the available genomic data (Fig. 1 and Supplementary Tables 1 and 2). The genetic time transect covers about 6,000 years, ranging from the Mesolithic and Neolithic (seventh and sixth millennia BC, n = 7), Eneolithic (fifth millennium BC, n = 11), Late Eneolithic and Early BA (EBA; fourth millennium BC, n = 20), EBA and Middle BA (MBA; third millennium BC, n = 51), to the final MBA and Late BA (LBA; second millennium BC, n = 42; Supplementary Table 1). Individuals (n = 26) who did not meet the quality criteria were excluded (Methods). The final dataset for population genetic analyses included 102 unrelated individuals, who were combined with published ancient and modern-day individuals (Supplementary Tables 3–5). Fig. 1: Geographical and chronological overview of individuals analysed in this study.  a, Map of the wider Caucasus region showing the locations of the 38 sampled sites and 131 individuals from this study and published data5 (Supplementary Tables 1 and 5). The number in parentheses indicates the studied individuals per site. The inset shows a magnified view of the area marked by the rectangle in the main image. Scale bars, 100 km (main image) and 10 km (inset). b, Timeline of the median 14C ages of newly reported (black outline) and published individuals (no outline), separated on the x axis into main genetic and geographic clusters (Steppe, Intermediate and Caucasus), as well as other published individuals from south of the Greater Caucasus for comparison. Colours in the piecharts (a), and colours and symbols in the timeline (b) represent sampled individuals associated with different archaeological cultural complexes, and these are used consistently across all figures (see Figs. 2 and 3, Extended Data Fig. 1, Supplementary Table 1 and Supplementary Fig. 1 for full site names and individual symbols). Grey bars correspond to the chronological chapters in the results section. The map was generated using Base Relief: Mapzen, OpenStreetMap, and rivers, lakes and borders were added using free vector and raster map data from Natural Earth (https://www.naturalearthdata.com). OpenStreetMap is open data, licensed under the Open Data Commons Open Database Licence by the OpenStreetMap Foundation. |
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Post by Admin on Nov 6, 2024 17:48:45 GMT
First we carried out principal component analysis (PCA) and ADMIXTURE analysis to qualitatively assess the genetic affinities of the ancient individuals (Methods and Extended Data Figs. 1 and 2). We substantiate the genetic differentiation observed between the steppe and mountain groups5, hereafter termed the Steppe and Caucasus clusters, and describe the formation and persistence of ancestries, including mixed Intermediate groups, which reflect dynamic phases of biological and cultural interaction resulting in the establishment and spread of pastoralism, first in the Pontic–Caspian and subsequently in the entire Eurasian steppe zone (Fig. 1). Finally, during the LBA period, we observe the dissolution of the main BA ancestry clusters and the formation of the ancestry found today in the people(s) of the North Caucasus region12,13.
The Mesolithic–Neolithic transition
The oldest individuals in this study are from Satanaj cave in Russia (SJG001, 6221–6082 cal BC), and from the early Neolithic site of Arukhlo in Georgia (5885–5476 cal BC, n = 4; Fig. 1). SJG001 predates the arrival of the Near Eastern Neolithic into the Caucasus and overlaps with Eastern European hunter-gatherers (EHGs) in PC space, despite being geographically close (about 50 km) to Caucasus hunter-gatherer (CHG) sites in the South Caucasus, whose individuals carry a different genetic ancestry profile7 (Fig. 2a). We find that SJG001 and EHG individuals from Karelia form a clade with respect to CHG individuals and other test populations (Extended Data Fig. 3a and Supplementary Tables 6 and 7). Using formal ancestry modelling with qpAdm, we were able to successfully model SJG001 with either Karelia_EHG or Sidelkino_EHG ancestry as a single source (Fig. 2c and Supplementary Table 8).
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Post by Admin on Nov 7, 2024 19:36:11 GMT
Fig. 2: Genetic overview of the seventh to fourth millennium BC.  a,b, PCA of newly produced ancient individuals (with outline) and individuals from previous publications (no outline) from the seventh and fifth millennium BC (a) and from the fourth millennium BC (b), projected onto 102 modern-day populations (grey dots). The dashed arrows in a represent the observed admixture clines between central Anatolian Neolithic and CHG (brown), between CHG and EHG (light green), and between Eneolithic_Caucasus and EHG ancestry-carrying Steppe groups (dark green), respectively. The dashed pink arrow in b represents an observed cline of mixture between Maykop-associated Caucasus groups and those carrying WSHG ancestry in the steppe. The corresponding labels and groupings are listed in Supplementary Table 5. c,d, Sankey diagram of genetic ancestry modelling for the seventh to fifth millennium BC (c) and fourth millennium BC (d) individuals from the Caucasus region with temporally and geographically proximal sources. The admixture proportions (as percentages) are indicated on each ancestry flow, with sources on the left and target populations on the right, and P values for each model in brackets under the population names (Supplementary Tables 8, 10 and 13). The suffixes in the group labels present archaeological time periods and geographical regions: WHG, Western hunter-gatherer; SHG, Scandinavian hunter-gatherer; MN, Middle Neolithic; C, Chalcolithic; EC, Early Chalcolithic; LC, Late Chalcolithic. Çatalhöyük_N is shown as Anatolia Neolithic, Tell Kurdu is shown as Anatolia EC and Jordan_PPNB and Jordan_PPNC are shown as Levant PPN. By contrast, the four Neolithic individuals from Arukhlo (ARO and AO2, Georgia_Neolithic) together with Armenia_N (with N denoting Neolithic) and Azerbaijan_LN (with LN denoting Late Neolithic) form a genetic cline between CHGs and central Anatolian Neolithic individuals (for example, Çatalhöyük), who themselves fall on a cline between Anatolian and Levantine ancestries14,15,16 (Fig. 2a and Extended Data Figs. 3b and 4). Thus, we modelled all Neolithic groups from the region using Anatolia_PPN (with PPN denoting pre-pottery Neolithic), Levant_PPN and CHG-Iran_N as distal ancestry sources (Fig. 2c, Extended Data Fig. 5 and Supplementary Table 8), and find that Georgia_Neolithic and Armenia_Aknashen_N carry the highest proportion of CHG-like ancestry, whereas Armenia_MasisBlur_N and Azerbaijan_LN carry more Levant_PPN-related ancestry. However, we also tested two-way mixture models between Anatolian or Levantine Neolithic groups and CHG and find that Georgia_Neolithic can be modelled as a two-way mixture between CHG and Çatalhöyük_N (shown as Anatolia Neolithic in Fig. 2a) or Tell Kurdu (Fig. 2c), but not with PPN groups from central Anatolia, Levant and Mesopotamia or Neolithic Northwest Anatolia. |
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Post by Admin on Nov 8, 2024 19:04:34 GMT
Eneolithic
During the Eneolithic period (4900/4700–3900 BC), a settled Near Eastern Neolithic lifestyle was introduced on the northern flanks of the Caucasus in association with the Darkveti–Meshoko culture (4500–4000 BC)5. Subsequently, the steppe zone further north was populated by transitional forager-pastoralist groups of the lower Volga Khvalynsk Eneolithic culture17. Adding genome-wide data from eight new individuals allows us to describe the formation of the Eneolithic groups in the North Caucasus steppe zone. We observe the earliest formation of Steppe ancestry, resulting from the gradual mixture of EHG-like ancestry with CHG-like ancestry from the south. Together with published Eneolithic and Khvalynsk individuals5,18, the newly reported Steppe_Eneolithic individuals form a genetic cline in PC space between EHG and CHG (Fig. 2a). f4-statistics show that Steppe_Eneolithic individuals from the North Caucasus have a higher affinity to CHG than individuals from Khvalynsk (Extended Data Figs. 4 and6 and Supplementary Table 9), and can be modelled as 55% CHG-like and 45% EHG-like ancestry (Supplementary Table 10).
We thus confirm the emergence of two distinct genetic clusters on the basis of PCA and ADMIXTURE, the Steppe cluster along the EHG–CHG cline and the mountain-oriented Caucasus cluster on the cline from Anatolia Neolithic to CHG-Iran_N (Fig. 2a, Extended Data Figs. 1 and 2 and ref. 5). Using the new Georgia_Neolithic data, we reassess the genetic ancestry of agropastoral Darkveti–Meshoko Caucasus_Eneolithic individuals from the Northwest Caucasus, which we model as a two-way mixture of Georgia_Neolithic (51% ± 6) and CHG (49% ± 6) ancestries (Fig. 2c, Extended Data Fig. 4 and Supplementary Table 10).
The individuals from Nalchik (NCK001 4531–4359 cal BC; NCK002 4930–4686 cal BC), labelled as Eneolithic_intermediate, fall between the Steppe and Caucasus groups in the PCA, suggesting gene flow between these groups. Indeed, ADMIXTURE and f4-statistics show that Nalchik individuals carry Caucasus ancestry, but also EHG-like ancestry (Fig. 2d, Extended Data Fig. 2 and Supplementary Tables 9 and 10). This means that the EHG–CHG cline and Caucasus ancestry16 must have already been formed by the time the ancestors of Nalchik met. Further, it limits the time frame of this mixture to the early fifth millennium BC and anticipates an axis of interaction that intensifies in the fourth millennium BC. Using DATES19, we estimate admixture dates for groups of both clusters and find that the Anatolia Neolithic to CHG-Iran_N cline formed around 6300–6000 BC, consistent with previous estimates16, and the EHG–CHG cline formed around 5800–5300 BC (Extended Data Fig. 5c and Supplementary Table 11).
Of note, KHB003 (4318–4057 cal BC) from the western-most site has a higher genetic affinity to Western hunter-gatherer (WHG) and Anatolia Neolithic-like ancestry (|Z| > 3), and can be modelled as a two-way mixture between CHG and Ukraine_Neolithic (Fig. 2d and Supplementary Tables 9 and 10).
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