Post by Admin on Nov 16, 2024 19:23:23 GMT
Discussion
We observe two genetically distinct populations in the Caucasus region before the Neolithic transition. SJG001 shares a close genetic affinity to hunter-gatherer groups from Karelia and the Samara region, as opposed to the geographically closer Ukraine_Mesolithic and Neolithic individuals, attesting to a lasting legacy of EHG ancestry across a large area of eastern Europe6. The lack of genetic admixture from the south opposes ideas of immigration of Epipalaeolithic groups from the Fertile Crescent, as proposed on the basis of similar lithic industries29,30. By contrast, groups carrying CHG-related ancestry must have persisted in the South Caucasus, as this ancestry is a source for Georgia_Neolithic. This cline between Anatolian Neolithic and CHG-like groups echoes the purported origin of the Neolithic expansion from the Fertile Crescent to the intermontane valleys in the Lesser Caucasus31,32 and shows that expanding Neolithic groups interacted early and intensively with local groups. The earliest sites in the Kura and Araxes valleys date to 6000/5900 BC. The individuals from Arukhlo reflect the rapid assimilation of the initial immigrants, which contrasts with the limited interaction between expanding farmers and WHG in Europe. The local CHG-like ancestry is also still detectable in individuals from Menteshtepe (Azerbaijan)33 and Akanashen (Armenia)15.
Neolithic lifeways emerged on the northern flanks of the Greater Caucasus among Eneolithic Darkveti–Meshoko agropastoral pioneers who share ancestry with South Caucasus populations. About 4300 BC, a different population, culturally related to the Khvalynsk Eneolithic17,34, arose in the Pontic–Caspian steppe further to the north and built the first burial mounds. This marks the first appearance of Steppe ancestry in the region, formed through pre-Neolithic hunter-gatherer interactions before the emergence of the Darkveti–Meshoko groups, whose ancestry contains Anatolian Neolithic ancestry not found in Steppe groups. The initial formation of Steppe ancestry dates to the mid-sixth millennium BC and is thus consistent with the described sequence of events. KHB003 from Khutor Belyy reflects genetic interaction of Steppe groups with peoples along the eastern parts of the Black Sea35, a trajectory that later became more important during the Yamnaya period. The oldest Eneolithic and genetically intermediate individuals from the cemetery of Nalchik provide a temporal constraint for the preceding CHG-related gene flow to the north. However, placing these Eneolithic events in sequence is challenged by radiocarbon dating reservoir effects, a problem that to some degree also affects BA pastoralist groups36,37. The earliest interaction between Steppe and Caucasus groups also extended to the south (for example, Areni 1 in Armenia)24. The consumption of dairy products by the Steppe_Eneolithic individuals KUG007 and PG2001 (ref. 2) and the presence of caprine teeth ornaments at Nalchik graves34 suggest that incipient pastoral economies may have facilitated these contacts in the Eurasian steppe2,38. Future genetic studies of domesticated animals will probably clarify the origins of the animals and related pastoral technologies that had already advanced to the mountains of Central Asia and Mongolia in the early third millennium BC (refs. 39,40).
The fourth millennium BC emergence of Maykop traditions in the Caucasus mountains and piedmonts signifies a clear cultural transition, whereas Eneolithic traditions persisted in the neighbouring steppe41. We observe five genetically distinguishable and largely contemporaneous groups. All piedmont-associated Maykop individuals carry Caucasus ancestry inherited from southern Neolithic and Eneolithic groups, which was probably maintained by keeping close kinship ties in cohesive communities, also reflected in shared architectural construction features in some Maykop mounds. By contrast, the genetic variability and scarcity of close biological relationships in the four Steppe Eneolithic groups suggest different and more flexible kin structures, which echo the persistence of varying cultural practices41.
For all groups, however, the archaeological record supports the transfer of Maykop material culture and social practices from the piedmonts into the steppe25,38, and the alternating use of the same mounds by different genetic groups suggests cultural interconnectedness. As sheep dairying practices became more prominent during this period2, isotope data from about 3500 BC onwards show a separation of grazing lands between communities in piedmont and steppe environments42. Maykop contexts show that the cultural interactions persisted for about 1,000 years, whereas the actual Caucasus cluster population (Maykop_main) did not spread and largely avoided intermarriage with Steppe groups. Innovations such as cattle-drawn wheeled transport and initial steps towards horse domestication gradually boosted mobility and herd management43,44. The clockwise tilt in the genetic cline of Late_Steppe_Eneolithic individuals from an EHG–CHG axis to an WSHG–Maykop axis is thus notable, as it encompasses additional WSHG ancestry, which is also found at Botai in Central Asia, another area of incipient equid domestication11,44,45. The genetic affinity of the Steppe_Maykop to eastern groups reflects the opening of the Eurasian steppe, even though this link is enigmatic and not yet related to any known archaeological phenomenon. Other technological innovations also started to spread, such as grassland-adapted sheep for dairying2, wheels and wagons43,46, and possibly wool as a material for insulating clothes and mobile architecture47. The display of wealth in graves was also soon transferred westwards, as indicated by close cultural links to Usatovo groups in the northwestern Black Sea area48. Indeed, the genetic profiles of several Steppe_Eneolithic individuals attest to contact with groups at the region’s western periphery and form the genetic substrate from which the third millennium BC Pontic–Caspian steppe pastoralists later emerged21. The horizon of combined innovations in the North Caucasus enabled the emergence of pastoralism and the dynamic modes of interaction, connectivity and mobility that subsequently spread across larger geographic regions, bridging the Caucasus region, the Pontic–Caspian steppe and Europe with lands in Central and Inner Asia10.
Genetic and archaeological evidence combined offer a perspective on the consolidation of pastoral economies in the third millennium BC, including homogenization of the Steppe ancestry profile and the emergence of Yamnaya groups. Notably, members of culturally distinct NCC and Catacomb communities25 also fall into this homogeneous genetic group. Moreover, we find individuals carrying Steppe ancestry at sites in the Caucasus mountains5, which suggests that groups with Caucasus ancestry had retreated higher into the mountains. The scarcity of closely related Steppe individuals is remarkable, given that some stem from narrow burial sequences within one mound. Combined with an elevated parental background relatedness, this suggests a form of social organization and kinship that regulates exogamy within a relatively small effective population. The Western Eurasian steppe pastoralists, best represented by the Yamnaya culture, stabilized and expanded their economy based on multispecies dairy products2,49,50 and wheeled vehicle mobility46, and spread their sustainable, permanent and self-supporting mobile lifestyle across the Eurasian steppe39,40,51.
By contrast, the contemporaneous Caucasus population is represented only by individuals of the Kura–Araxes culture at present. In parallel to the pastoralist expansions across the Eurasian steppe, Kura–Araxes groups expanded into the Levant and today’s Iran52, which is reflected in the genetic shift towards Iranian BA populations. We observe no genetically intermediate individuals, but also acknowledge sampling gaps for this epoch.
The second millennium BC is marked by a decline of activity and population density in the North Caucasus steppe, and a total abandonment by about 1700 BC (ref. 2), possibly brought about by climatic shifts and overexploitation of ecologically fragile steppe habitats following the 4.2 kyr BP environmental crisis22,53. The homogeneous Steppe ancestry cluster of the preceding third millennium BC dissolves into several post-Catacomb groups, who show genetic affinities to Central Asia, as seen among the Lola, or to the northwestern Srubnaya. Interaction between mountain and steppe cultures also intensified during this period, evident in material culture and the genetic shift of the Caucasus groups towards the Steppe cluster and vice versa. This was previously interpreted as an expansion of mountain populations into the Pontic–Caspian steppe between 2200 BC and 1700 BC (ref. 22), but we observe instead an absorption of Steppe groups into Caucasus groups, probably driven by the steppe habitats becoming increasingly inhospitable.
From these developments, a pan-Caucasian mountain interaction sphere from dolmens in the northwest (Shushuk) to Dagestan (Ginchi) emerged that culturally represents the LBA23 and also a genetic ancestry profile that still persists in the North Caucasus today12,13. This process anticipated the integration of the mountain populations in the succeeding LBA and Early Iron Age cultures23, and marked the transition from a mobile BA steppe pastoralist economy to a more sedentary and complex agropastoral mountain economy54.
For two millennia, mobile pastoralism dominated lifeways on the great expanses of steppe extending northwards from the Caucasus mountains. Fuelled by technological innovations such as wheeled transport and dairy pastoralism, as well as emerging horse husbandry, steppe populations from the Caucasus–Steppe interface exerted a large influence on the Eurasian landmass, leaving far-flung genetic and cultural footprints that remain even today. Understanding the dynamic and complex population interactions that shaped the region’s most influential BA groups, such as the Maykop, Yamnaya and Kura–Araxes, is key to reconstructing the population history of both Europe and Asia. Here we reveal the genetic events that led to the formation of these groups and trace the region’s history through its ultimate decline and abandonment about 1700 BC, even as the region’s mobile pastoralism legacy continued to spread and flourish elsewhere55.
We observe two genetically distinct populations in the Caucasus region before the Neolithic transition. SJG001 shares a close genetic affinity to hunter-gatherer groups from Karelia and the Samara region, as opposed to the geographically closer Ukraine_Mesolithic and Neolithic individuals, attesting to a lasting legacy of EHG ancestry across a large area of eastern Europe6. The lack of genetic admixture from the south opposes ideas of immigration of Epipalaeolithic groups from the Fertile Crescent, as proposed on the basis of similar lithic industries29,30. By contrast, groups carrying CHG-related ancestry must have persisted in the South Caucasus, as this ancestry is a source for Georgia_Neolithic. This cline between Anatolian Neolithic and CHG-like groups echoes the purported origin of the Neolithic expansion from the Fertile Crescent to the intermontane valleys in the Lesser Caucasus31,32 and shows that expanding Neolithic groups interacted early and intensively with local groups. The earliest sites in the Kura and Araxes valleys date to 6000/5900 BC. The individuals from Arukhlo reflect the rapid assimilation of the initial immigrants, which contrasts with the limited interaction between expanding farmers and WHG in Europe. The local CHG-like ancestry is also still detectable in individuals from Menteshtepe (Azerbaijan)33 and Akanashen (Armenia)15.
Neolithic lifeways emerged on the northern flanks of the Greater Caucasus among Eneolithic Darkveti–Meshoko agropastoral pioneers who share ancestry with South Caucasus populations. About 4300 BC, a different population, culturally related to the Khvalynsk Eneolithic17,34, arose in the Pontic–Caspian steppe further to the north and built the first burial mounds. This marks the first appearance of Steppe ancestry in the region, formed through pre-Neolithic hunter-gatherer interactions before the emergence of the Darkveti–Meshoko groups, whose ancestry contains Anatolian Neolithic ancestry not found in Steppe groups. The initial formation of Steppe ancestry dates to the mid-sixth millennium BC and is thus consistent with the described sequence of events. KHB003 from Khutor Belyy reflects genetic interaction of Steppe groups with peoples along the eastern parts of the Black Sea35, a trajectory that later became more important during the Yamnaya period. The oldest Eneolithic and genetically intermediate individuals from the cemetery of Nalchik provide a temporal constraint for the preceding CHG-related gene flow to the north. However, placing these Eneolithic events in sequence is challenged by radiocarbon dating reservoir effects, a problem that to some degree also affects BA pastoralist groups36,37. The earliest interaction between Steppe and Caucasus groups also extended to the south (for example, Areni 1 in Armenia)24. The consumption of dairy products by the Steppe_Eneolithic individuals KUG007 and PG2001 (ref. 2) and the presence of caprine teeth ornaments at Nalchik graves34 suggest that incipient pastoral economies may have facilitated these contacts in the Eurasian steppe2,38. Future genetic studies of domesticated animals will probably clarify the origins of the animals and related pastoral technologies that had already advanced to the mountains of Central Asia and Mongolia in the early third millennium BC (refs. 39,40).
The fourth millennium BC emergence of Maykop traditions in the Caucasus mountains and piedmonts signifies a clear cultural transition, whereas Eneolithic traditions persisted in the neighbouring steppe41. We observe five genetically distinguishable and largely contemporaneous groups. All piedmont-associated Maykop individuals carry Caucasus ancestry inherited from southern Neolithic and Eneolithic groups, which was probably maintained by keeping close kinship ties in cohesive communities, also reflected in shared architectural construction features in some Maykop mounds. By contrast, the genetic variability and scarcity of close biological relationships in the four Steppe Eneolithic groups suggest different and more flexible kin structures, which echo the persistence of varying cultural practices41.
For all groups, however, the archaeological record supports the transfer of Maykop material culture and social practices from the piedmonts into the steppe25,38, and the alternating use of the same mounds by different genetic groups suggests cultural interconnectedness. As sheep dairying practices became more prominent during this period2, isotope data from about 3500 BC onwards show a separation of grazing lands between communities in piedmont and steppe environments42. Maykop contexts show that the cultural interactions persisted for about 1,000 years, whereas the actual Caucasus cluster population (Maykop_main) did not spread and largely avoided intermarriage with Steppe groups. Innovations such as cattle-drawn wheeled transport and initial steps towards horse domestication gradually boosted mobility and herd management43,44. The clockwise tilt in the genetic cline of Late_Steppe_Eneolithic individuals from an EHG–CHG axis to an WSHG–Maykop axis is thus notable, as it encompasses additional WSHG ancestry, which is also found at Botai in Central Asia, another area of incipient equid domestication11,44,45. The genetic affinity of the Steppe_Maykop to eastern groups reflects the opening of the Eurasian steppe, even though this link is enigmatic and not yet related to any known archaeological phenomenon. Other technological innovations also started to spread, such as grassland-adapted sheep for dairying2, wheels and wagons43,46, and possibly wool as a material for insulating clothes and mobile architecture47. The display of wealth in graves was also soon transferred westwards, as indicated by close cultural links to Usatovo groups in the northwestern Black Sea area48. Indeed, the genetic profiles of several Steppe_Eneolithic individuals attest to contact with groups at the region’s western periphery and form the genetic substrate from which the third millennium BC Pontic–Caspian steppe pastoralists later emerged21. The horizon of combined innovations in the North Caucasus enabled the emergence of pastoralism and the dynamic modes of interaction, connectivity and mobility that subsequently spread across larger geographic regions, bridging the Caucasus region, the Pontic–Caspian steppe and Europe with lands in Central and Inner Asia10.
Genetic and archaeological evidence combined offer a perspective on the consolidation of pastoral economies in the third millennium BC, including homogenization of the Steppe ancestry profile and the emergence of Yamnaya groups. Notably, members of culturally distinct NCC and Catacomb communities25 also fall into this homogeneous genetic group. Moreover, we find individuals carrying Steppe ancestry at sites in the Caucasus mountains5, which suggests that groups with Caucasus ancestry had retreated higher into the mountains. The scarcity of closely related Steppe individuals is remarkable, given that some stem from narrow burial sequences within one mound. Combined with an elevated parental background relatedness, this suggests a form of social organization and kinship that regulates exogamy within a relatively small effective population. The Western Eurasian steppe pastoralists, best represented by the Yamnaya culture, stabilized and expanded their economy based on multispecies dairy products2,49,50 and wheeled vehicle mobility46, and spread their sustainable, permanent and self-supporting mobile lifestyle across the Eurasian steppe39,40,51.
By contrast, the contemporaneous Caucasus population is represented only by individuals of the Kura–Araxes culture at present. In parallel to the pastoralist expansions across the Eurasian steppe, Kura–Araxes groups expanded into the Levant and today’s Iran52, which is reflected in the genetic shift towards Iranian BA populations. We observe no genetically intermediate individuals, but also acknowledge sampling gaps for this epoch.
The second millennium BC is marked by a decline of activity and population density in the North Caucasus steppe, and a total abandonment by about 1700 BC (ref. 2), possibly brought about by climatic shifts and overexploitation of ecologically fragile steppe habitats following the 4.2 kyr BP environmental crisis22,53. The homogeneous Steppe ancestry cluster of the preceding third millennium BC dissolves into several post-Catacomb groups, who show genetic affinities to Central Asia, as seen among the Lola, or to the northwestern Srubnaya. Interaction between mountain and steppe cultures also intensified during this period, evident in material culture and the genetic shift of the Caucasus groups towards the Steppe cluster and vice versa. This was previously interpreted as an expansion of mountain populations into the Pontic–Caspian steppe between 2200 BC and 1700 BC (ref. 22), but we observe instead an absorption of Steppe groups into Caucasus groups, probably driven by the steppe habitats becoming increasingly inhospitable.
From these developments, a pan-Caucasian mountain interaction sphere from dolmens in the northwest (Shushuk) to Dagestan (Ginchi) emerged that culturally represents the LBA23 and also a genetic ancestry profile that still persists in the North Caucasus today12,13. This process anticipated the integration of the mountain populations in the succeeding LBA and Early Iron Age cultures23, and marked the transition from a mobile BA steppe pastoralist economy to a more sedentary and complex agropastoral mountain economy54.
For two millennia, mobile pastoralism dominated lifeways on the great expanses of steppe extending northwards from the Caucasus mountains. Fuelled by technological innovations such as wheeled transport and dairy pastoralism, as well as emerging horse husbandry, steppe populations from the Caucasus–Steppe interface exerted a large influence on the Eurasian landmass, leaving far-flung genetic and cultural footprints that remain even today. Understanding the dynamic and complex population interactions that shaped the region’s most influential BA groups, such as the Maykop, Yamnaya and Kura–Araxes, is key to reconstructing the population history of both Europe and Asia. Here we reveal the genetic events that led to the formation of these groups and trace the region’s history through its ultimate decline and abandonment about 1700 BC, even as the region’s mobile pastoralism legacy continued to spread and flourish elsewhere55.