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Post by Admin on Jan 24, 2024 19:31:52 GMT
Around half of the 45 individuals between ~1-250 CE can be fitted with qpAdm models featuring only Balkan Iron Age groups (Figure 2A) and are characterized by a high frequency (5 out of 10) of Y-chromosome lineage E-V13 (Data S1, section 2), which has been hypothesized to have experienced a Bronze-to-Iron Age expansion in the Balkans28. These individuals, sampled from Roman towns such as Viminacium, Tragurium (Trogir) and Mursa (Osijek), are consistent with being direct descendants of local Balkan Iron Age populations (Figure 2A), pointing to a high degree of integration of the local population into Roman society. Despite the exceptional number of Roman colonies in the region, and the large military presence along this frontier, there is little ancestry contribution from populations long established in the Italian Peninsula, a pattern exemplified by the almost complete absence in our Balkan transect of Y-chromosome lineage R1b-U152, the most common paternal lineage in Bronze Age and Iron Age populations in the Italian Peninsula15,16,29. The prevalence of cremation burials in the earliest centuries could bias the sample, but even after the transition to inhumation burial around the 2nd century, ancestry contributions from populations of Italian descent are not detectable. Rome’s cultural impact on the Middle Danube was deep, but our findings suggest that it was not accompanied by large-scale population movement from the metropole, at least by the descendants of central Italian Iron Age populations. Figure 2. A diversity of ancestral origins. (A) By-individual estimates of Iron Age Balkan, West Anatolian/Levantine, and African-related ancestry proportions between 0-1500 CE, computed with qpAdm. Two pairs of individuals buried in the same sarcophagi at Rit Necropolis (Viminacium) are connected through black lines. (B) δ15N and δ13C stable isotope values (Data S2, Table 9) of ancient Balkan individuals between 0-500 CE obtained from tooth roots, plotted alongside published environmental data and humans from related geographic and chronological contexts34,44-47. Individuals buried at the same necropolis are connected through lines. (C) Oil lamp depicting an eagle found on individual G-103’s (I15499) grave at Pirivoj, Viminacium. (D) Sarcophagus of grave 148 at Rit Necropolis, Viminacium. The Roman Empire did, however, stimulate demographic change in the Balkans. In this early period, ~1/3 of the individuals (15 out of 45) fall beyond the Balkan clines in PCA (Figure 1C; Figure S4) but close to Near Easterners, and can be modeled as deriving their ancestry predominantly from Roman/Byzantine populations from Western Anatolia and, in one case, from Northern Levantine groups (Figure 2A; Data S2, Table 6). Most of these individuals were excavated at four different Viminacium necropolises, but we also found them at other urban centers such as Tragurium (Trogir) and Iader (Zadar). A very strong demographic shift towards Anatolia is also evident in Rome and central Italy during the same period15,25 and demonstrates long-distance mobility plausibly originating from the major eastern urban centers of the Empire such as Ephesus, Corinth, or Byzantium/Constantinople; our results show that these migrants had a major demographic impact not only on the Imperial capital but also on other large towns on the Empire’s northern periphery. Our data also provide insights concerning the social dynamics of this demographic process. Unlike the Balkan Iron Age ancestry group whose sex ratio was evenly balanced (11 females out of 22 individuals), the 12 adult individuals with full Anatolian/Levantine ancestry included only 2 women (p = 0.019 for a one-sided binomial test for more males than females). This points to a larger contribution of Near Eastern men, but could also result from different burial customs between the sexes. People with Anatolian ancestry and people with local Balkan ancestry were not spatially segregated in burial nor, for the most part, culturally distinct in burial customs or grave goods. They admixed and were buried at the same necropolises, even side-by-side as in tomb G-148 at Rit necropolis (Figure 2D). However, the evidence may also point to some degree of social stratification, since all 3 individuals at the Rit necropolis of Anatolian origin were buried in stone sarcophagi with exceptionally rich grave goods (Figure 2D and Data S1, section 1)30. The main source of migrants to the region shifted away from Anatolia after ~300 CE (Figure 2A), but together with the ancestral legacy of local Balkan Iron Age groups, Anatolian-related ancestry persisted in admixed form into the later Medieval individuals (Figure 2A) with a mean of 23% (95% CI = 17-29%), indicating that this was a deep and lasting demographic impact.
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Post by Admin on Jan 26, 2024 19:34:40 GMT
Migrants from sub-Saharan Africa and North Africa Our newly reported data also revealed sporadic long-distance mobility. Three men who likely lived in the 2nd or 3rd centuries CE fell outside European and Near Eastern variability (Figure S1), close to present-day and ancient Africans (Figure S2A). Proximal qpAdm modeling confirmed these observations (Figure 2A; Data S2, Table 6) with 33% and 100% North African ancestry for individuals I26775 (Iader) and I32304 (Viminacium Pećine), respectively, while I15499 (Viminacium Pirivoj) could be modeled using only ancient East African populations, supporting an East African ancestral origin and agreeing with his uniparental markers mtDNA L2a1j and Y-chromosome E1b-V32, both common in East Africa today28,31. The individual of East African ancestry was buried with an oil lamp depicting Jupiter-related eagle iconography (Figure 2C; Data S1, section 1), not a common finding in Viminacium graves32. Isotopic analysis of tooth roots showed that he was also an outlier with respect to dietary habits during childhood (Figure 2B), with elevated δ15N and δ13C values indicating the likely consumption of marine protein sources33, unlike individuals from Pirivoj and other necropolises whose values (Figure 2B) were similar to the Roman-Period population from Sirmium34 and consistent with a largely C3-based diet with a significant portion of animal protein consumption33. Thus, he likely spent his early years elsewhere, possibly in East Africa, the land of his ancestors; while we will never know his whole life story, whether as soldier, slave, merchant, or migrant, it encompassed a long journey that ended with his death in adolescence on the northern frontiers of the Roman Empire.
From internal to external migration during Late Antiquity Beginning in the 3rd or 4th century CE, we observe individuals who are admixed with ancestry related to Central/Northern Europeans and Pontic-Kazakh Steppe populations (Figure 4A; Data S2, Table 6). These two ancestry types tend to colocalize in the same individuals, suggesting that the stream of migrants into the Balkans included people who were admixtures of these two sources, although there are some exceptions, such as two contemporaries from Viminacium, Pećine necropolis, who can be modeled as having 36-50% steppe-related ancestry without any contribution of Central/Northern European ancestry (Figure 1C and Data S2, Table 6). Individuals bearing these ancestries were buried at the same necropolises (such as Pećine and Više Grobalja at Viminacium) as individuals with predominantly local and Anatolian ancestries, often with overlapping radiocarbon dates, and displayed 42-55% of Balkan Iron Age-related ancestry (Data S2, Table 6). In contrast, only 2 out of 9 males belonged to Y-chromosome lineages found among individuals with a fully local ancestry profile (Data S1, section 2), with the rest belonging to three haplogroups: I1 and R1b-U106 with a strong Northern European distribution, and haplogroup R1a-Z93, which was common in the Steppe during the Iron Age and early 1st millennium CE35-37. Such discrepancy between the autosomal and Y-chromosome signals could be explained by a patrilineal social organization such as has been deduced for early Germanic societies38 that resulted in the persistence of the incoming male lineages, due to social selection for reproductive success among male offspring from these lineages, and its observation in the admixed individuals in our transect. People with these ancestry profiles present evidence of different dietary patterns, too, as shown by significantly elevated δ13C values (p = 0.001) for individuals bearing ancestry from Pontic-Kazakh Steppe groups (Figure 2B), likely pointing to a C4-rich diet39.
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Post by Admin on Jan 27, 2024 20:42:25 GMT
Figure 4. Demographic impact of Migration Period and Early Medieval events. (A) Changes in Central/Northern European, Pontic-Kazakh Steppe and Eastern European-related ancestry proportions between 0-1500 CE, computed with qpAdm. A mother and her son are connected through a red line. (B) Proportions of Eastern-European-related ancestry (in black) for present-day Balkan and Aegean populations. The appearance of individuals with admixed Central/Northern European and Pontic-Kazakh steppe ancestry inside the Roman Empire in late antiquity reflects the Roman encounter with various trans-frontier populations in this period. Notably, many individuals reflect a prior process of population admixture between these two sources that likely occurred beyond the Roman frontier, perhaps indicative of, e.g., the formation of diverse confederations under Gothic leadership40. Furthermore, although the Roman Empire intermittently lost military control of this frontier from the middle of the third century on, it is noteworthy that many individuals with these ancestries appear integrated into Roman society well before the final breakdown of Roman control of the region. This pattern confirms the importance of processes such as migration, recruitment, and settlement (whether sanctioned by the imperial government or not) in the demographic history of the region in late antiquity, a period of intense interaction and exchange across the Danube border41. It is also noteworthy that only 3 individuals show >80% ancestry related to Central/Northern European and Pontic-Kazakh steppe groups. Perhaps the fewer samples whose date range falls in the 6th century CE (n = 10) obscures the importance of direct migration of large, predominantly Germanic groups into the region. But it is just as important to observe that many individuals belonging to archaeological contexts identified by cultural criteria (Data S1, section 1) as belonging to various Germanic groups reflect a process of admixture with local populations. At Kormadin, for instance, in what has conventionally been identified as a “Gepid” cemetery, out of four individuals tested we identified two who model as completely local Iron Age Balkan ancestry and two, including one child aged 5-7 years, who display local Iron Age Balkan, Central/Northern European and Pontic-Kazakh steppe ancestry. It is also unexpected to find that Central/North European and Pontic-Kazakh steppe ancestries vanished after 700 CE (95% CI for the sum of these two ancestry proportions = 0-3%) (Figure 4A; Data S2, Table 6). While the relatively small differentiation between Central/North European and Eastern European ancestries could have resulted in the misassignment of small proportions of Central/North European ancestry as Eastern European ancestry, this result is supported by the complete absence (Data S1, section 2) of Y-chromosome lineages clearly associated with Central/North European and Pontic-Kazakh steppe ancestry (I1, R1b-U106 and R1a-Z93) in the 24 individuals in our transect who lived after 700 CE (95% CI for the frequency of those haplogroups = 0-12%). While this absence could reflect unknown sampling bias, it suggests that the population size of incoming Central/North European groups may have been limited as compared to the local Iron Age population, and/or that selective demographic processes—out-migration, differential mortality due to urbanism or military service—acted to prevent a long-lasting demographic impact of these groups.
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Post by Admin on Jan 29, 2024 21:07:51 GMT
Slavic migrations and the formation of the present-day Balkan gene pool By 700 CE, a new type of ancestry appears across all the Balkan regions covered by our sampling. In a PCA projection onto diverse West Eurasian populations (Figure 1C), these individuals fall at similar positions as the earlier group with Central/Northern European and Pontic-Kazakh steppe-related ancestry. However, we can distinguish their ancestry with a PCA setup more sensitive to recent drift separating Central/Northern and Eastern European populations (Figure 3A). Several Balkan individuals before 700 CE plot close to present-day Central and Northern European Germanic-speaking populations, overlapping individuals from Langobard-associated cemeteries in Hungary and Northern Italy18 displaying Central/Northern European-related ancestry (CNE_EarlyMedieval). After 700 CE, we observe a clear shift toward present-day Eastern European Slavic-speaking populations in the ancient Balkan transect, a shift mirrored by present-day Balkan populations (Figure 3A). Accordingly, Eastern European-related populations share more alleles (Z = 9.85) with Balkan individuals after 700 CE as compared to before 700 CE (Figure 3B). The differential affinities of Balkan individuals with the strongest Central/Northern European shift in PCA (Z = 1.99) and Balkan individuals with the strongest Eastern European shift in PCA (Z = −3.41), is evident using f4-statistics of the form f4 (OldAfrica, Test; Eastern European-related, Central/Northern European-related) (Figure 3B). Corroborating these results, qpAdm models (Data S1, section 4) with Central/Northern European and Pontic-Kazakh steppe groups yield a very poor fit (p = 2.70 × 10−15; Data S2, Table 7) for the group of Balkan individuals with the strongest Eastern European shift, and we were able to obtain a better fit with variable proportions of Balkan Iron Age-related, Anatolian-related and Eastern European-related ancestry (p = 0.049; Data S2, Table 7). As an Eastern European-related proxy, we used a group of early medieval individuals excavated in western Hungary, the Czech Republic, eastern Austria and Western Slovakia (CEE_EarlyMedieval). This group fell within the variation of present-day Eastern European Slavic-speaking populations, very close to the Balkan individuals in our dataset with the strongest Eastern European-related shift (Figure 3A; Figure S3). Figure 3. Arrival of ancestry related to Eastern European populations after 700 CE. (A) PCA computed on present-day Central, Northern and Eastern Europeans. Present-day Balkan individuals and ancient individuals were projected onto the PCs. Ancient Balkan individuals are shown as red and blue diamonds and other relevant ancient populations are shown as colored polygons including all individuals in each population. (B) f4-statistics assessing differential affinities to Central/Northern- and Eastern European-related groups. Central/Northern European-related includes individuals from two Langobard-associated cemeteries in Hungary and Northern Italy displaying Central/Northern European-related ancestry (CNE_EarlyMedieval) and Bronze and Iron Age individuals from the Netherlands (Data S2, Table 3). Eastern European-related includes CEE_EarlyMedieval and Bronze Age individuals from Latvia and Lithuania. Test populations are shown in the y-axis. Error bars represent one standard error. We present evidence that Eastern European ancestry was sporadically present in the Balkans long before the Slavic migrations of late antiquity. Indeed, a woman who probably died in the 2nd or 3rd centuries CE and was buried at Više Grobalja presents unmixed Eastern European ancestry (Figure 4A), offering a remarkable illustration of how small-scale individual percolation into the dynamic economy of the Roman Empire may have preceded larger-scale migration. The vast majority of the individuals with Eastern European ancestry in our dataset appear in the 7th-10th centuries and are of admixed ancestry (Figure 4A); the Slavic migrations started as early as the 6th century42, and our dataset may not reflect the early phases, although it provides insights into its dynamics. Out of the seven Balkan individuals with more than 90% East European-related ancestry who were more likely to be migrants, three were females. This finding, together with a ~50/50 ratio of local versus non-local (R1a-Z282, I2a-L621 and Q1a-L715) Y-chromosome lineages (Data S1, section 2), hints at different social dynamics operating during this event as compared to previous periods: here females as well as males make major contributions. We have evidence of the interaction between the two groups at the individual level. At the fortified settlement of Brekinjova Kosa (Bojna, Croatia), two adult men dated to 770-890 cal CE were buried together in the same pit, the younger one with healed skull trauma and with a full Eastern European profile, and the older one with ancestry entirely deriving from Balkan Iron Age populations. Additionally, at the site of Dvorac (Nuštar, Croatia), a woman (Grave 52) with ~90% Eastern European ancestry had a son (Grave 50-A; 64% of this ancestry) (Figure 4A; Data S2, Table 6) with an unsampled man who, like the main group of individuals from the site, must have had ~30% Eastern European ancestry, demonstrating a direct case of incorporation of non-local women that could exemplify some of the social processes at play. The finding of a pair of 10th-century twins with southwestern European ancestry at Timacum Minus again demonstrates sporadic mobility from far-away regions in the Middle Danube. To explore whether the Eastern European ancestry signal persisted in present-day Balkan and Aegean populations, we attempted to model present-day groups (Data S1, section 5) by using the same qpAdm model used for the ancient individuals after 700 CE with Eastern European-related ancestry. Present-day Serbs, Croats, Bulgarians and Romanians yielded a similar ancestral composition as ancient individuals after 900 CE at sites such as Timacum Minus, Tragurium or Rudine necropolis at Viminacium, with ~50-60% Eastern European-related ancestry admixed with ancestry related to Iron Age Balkan populations and in some cases also a Roman Anatolian contribution (Figure 4B; Data S2, Table 8), implying substantial population continuity in the region over the last 1,000 years. The Eastern European signal significantly decreases in more southern modern groups but it is still present in populations from mainland Greece (~30-40%) and even the Aegean islands (4-20%). This confirms the observations from PCA (Figure 1C and and3A)3A) and previous genetic studies suggesting a substantial demographic impact in the southern Balkan Peninsula8 and the Aegean42. Discussion
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Post by Admin on Feb 1, 2024 22:08:57 GMT
Archaeogenetic studies are delivering new evidence that is transforming our understanding of human prehistory and prompting an intense and productive dialogue between geneticists and archaeologists. So far, relatively fewer studies focus on the historical period, that of writing, which requires engagement with written sources in addition to the material evidence. Triangulation of information from history, the archaeological study of material culture, and genetics opens new possibilities for understanding the human past, with each line of evidence not only providing unique information but helping to address biases deriving from other types of analysis. To aid in these goals, the supplement ‘Archaeological Overview’ to this study includes detailed and standardized historical and archaeological information for over twenty sites, along with contextual data for each grave with a newly reported genome. This deeper synthesis of historical, archaeological, and genetic data informs our interpretations, while the detailed site and grave reports allow others to refine our reconstructions or to extend them as future results become available.
The genomic transect of first-millennium individuals from the Balkan Peninsula presented here furnishes new insights into the long-term population dynamics of a region that was both a crucial frontier of the Roman Empire as well as an enduring geographic crossroads between east and west, north and south. The results emphasize the importance of continuing population change in historical times and the long-term shifts in the role of socio-political structures across the 1st millennium. The period of Roman control was dominated by internal migration, with sporadic but increasing long-distance migration from outside the territory of the Roman Empire; this pattern reversed in later centuries, with a relatively larger contribution from populations originating beyond the Danube corridor.
Broadly, our results suggest three phases in the population history of this region in the 1st millennium. First, the high Roman Empire (ca. 1-250 CE) saw the strong impact of Roman culture on the local Iron Age Balkan population. While this process was accompanied by little detectible contribution from populations with ancestry from the Italian Peninsula, there was significant migration by individuals of Anatolian/Eastern Mediterranean ancestry, either directly or through Italy, whose admixture would leave a long trail in later local populations. Meanwhile, militarization and/or economic vitality attracted migrants from further afield both within and beyond the Roman Empire. In some cases at least, the small-scale percolation of individuals preceded large-scale population movements of later centuries.
In the late Roman Imperial period (ca. 250-550) internal migration from within the empire lessened, while the presence of individuals with ancestry originating in populations from beyond the Danube frontier is evident. Admixture was pervasive both among groups originating beyond the frontier (notably Northern/Central Europeans and Pontic-Kazakh Steppe groups) as well as among these groups and the local population. While claims about the identity of individuals or groups have sometimes been made based on material culture discovered in burial contexts, DNA-based ancestry data can reveal the complex role of processes like migration and admixture behind individual and group histories (see above, for the example from Kormadin, where a "Gepid" cemetery certainly included individuals with local Iron Age-Balkan ancestry). The presence of North/Central European ancestry disappears in later periods, suggesting that individuals with this ancestry were relatively few or that historical processes (such as further migration or differential mortality) selectively reduced their contribution in later centuries. For generations, scholars of late Antique history have debated the extent to which the political transitions accompanying the end of Roman rule were fueled by demographic changes and whether these transitions were driven by ethnogenesis or mass migration. Our findings support a nuanced view in which both ethnogenesis and migration were important.
Today, speakers of Slavic languages represent the largest linguistic group in Europe, mainly inhabiting Eastern, Central and Southeastern Europe. Several aspects of their initial arrival in the Balkans are not yet well understood, such as their place of origin and timing, the mechanisms ranging from colonization, invasion, and infiltration, their degree of demographic impact in the region and the underlying reasons with demographic pressures, climate change and depopulation due to the Justinian Pandemic being postulated42,43. We document a clear signal of Eastern European-related gene flow in the vast majority of individuals in our dataset after 700 CE (n=49), likely associated with the arrival of Slavic-speaking populations according to historical and archaeological evidence42. Due to a gap in our sampling between 500-700 CE, we cannot determine the exact timing of the earliest arrivals, but the detection of individuals with full Eastern European ancestral origin during the 8th and 9th centuries points to a long process encompassing many generations, rather than a short-lived migration event. Unlike the earlier Central/Northern European gene-flow, genomic data are consistent with a major contribution of migrations of both sexes and with a long-lasting strong demographic impact in the region that extends to present-day populations. Nevertheless, our results rule out a complete demographic replacement, as we observe significant proportions of Iron Age Balkan-related and Anatolian-related ancestry across the Medieval period up to the present. These demographic processes of mobility and admixture generated an ancestry cline of present-day Balkan populations with relatively similar ancestry profiles but speaking languages from four different families, i.e. Latin, Slavic, Albanian and Greek, highlighting different cultural processes across the region despite many commonalities in their demographic history. Together, these processes created a regional ancestry profile by the end of the 1st millennium that largely endures across the region.
Limitations of the Study Like any historical evidence, this new genetic dataset has limitations. The main one concerns the inherent fragmentary nature of the archaeological record, impacting our study in three ways. First, the prevalence of cremation burial in the first and second century limits the size of the sample in the earliest phase and may bias the results toward a local population more likely to be inhumed. Second, the paucity of sixth-century samples may obscure the presence of populations from Northern/Central Europe who arrived in this later period as well as the earliest phases of the Slavic migrations. Third, urban populations are overrepresented in our study with respect to rural areas, which could be differentially impacted by the demographic processes described in our work. Additional genetic analyses across other Roman frontiers during and after the height of the Empire will help to understand how this ancient phase of globalization shaped the current demographic landscape of three continental regions.
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