Origin of the Romanians Mar 10, 2020 21:41:39 GMT
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Ancient human mitochondrial genomes from Bronze Age Bulgaria: new insights into the genetic history of Thracians
Alessandra Modi, Desislava Nesheva, Stefania Sarno, Stefania Vai, Sena Karachanak-Yankova, Donata Luiselli, Elena Pilli, Martina Lari, Chiara Vergata, Yordan Yordanov, Diana Dimitrova, Petar Kalcev, Rada Staneva, Olga Antonova, Savina Hadjidekova, Angel Galabov, Draga Toncheva & David Caramelli
Scientific Reports volume 9, Article number: 5412 (2019)
One of the best documented Indo-European civilizations that inhabited Bulgaria is the Thracians, who lasted for more than five millennia and whose origin and relationships with other past and present-day populations are debated among researchers. Here we report 25 new complete mitochondrial genomes of ancient individuals coming from three necropolises located in different regions of Bulgaria – Shekerdja mogila, Gabrova mogila and Bereketska mogila – dated to II-III millennium BC. The identified mtDNA haplogroup composition reflects the mitochondrial variability of Western Eurasia. In particular, within the ancient Eurasian genetic landscape, Thracians locate in an intermediate position between Early Neolithic farmers and Late Neolithic-Bronze Age steppe pastoralists, supporting the scenario that the Balkan region has been a link between Eastern Europe and the Mediterranean since the prehistoric time. Spatial Principal Component Analysis (sPCA) performed on Thracian and modern mtDNA sequences, confirms the pattern highlighted on ancient populations, overall indicating that the maternal gene pool of Thracians reflects their central geographical position at the gateway of Europe.
Bulgaria is situated in the eastern part of the Balkan Peninsula, at the connection point between Southeastern Europe, Eurasian steppe, Anatolia and the Aegean islands. The presence of modern humans in this region is attested starting from 40 kya by the Paleolithic series at Bacho Kiro and Temnata Dupka Caves1,2,3. Some archaeological sites associated with early farmers, as well as the earliest evidence of copper metallurgy in Europe, indicates that this area played a significant role both in the Neolithic and in the Metal Ages4. One of the best documented Indo-European civilizations that inhabited Bulgaria consists in the Thracians, whose cultural legacy is still evident in the modern society.
Different theories have been historically proposed about the origin of the Thracians. Today it is assumed that the Thracian culture emerged and formed in the early Bronze Age5,6,7, a period characterized by strong cultural changes and movements of people westward from the Steppe8. During the 5th and 4th millennium BCE, the inhabitants of the eastern region of Balkans were organized in different groups of indigenous people that, over time, were named under the single ethnonym of “Thracians”9,10,11. According to historical and archaeological sources, the Thracian culture flourished during the 2nd and 3rd millennia BCE12,13. The rich cultural and historical heritage, represented by fortresses and necropolises, as well as by the world-famous Panagyurishte, Valchitran, Lukovit and Rogozen treasures, dates back to this period. In the later periods, several populations (Greeks, Macedonians, Slavs and proto-Bulgarians) arrived in the Balkans, reaching the lands occupied by Thracians and mixing with them, thus influencing their cultural and biological identity11.
Genetic analyses on both autosomal variations14 and uniparental genetic markers15,16,17 of present-day Bulgarians, locate them between Eastern European and Mediterranean populations, with a particular affinity to the neighboring groups from Greece and the Balkans16. In addition, the Bulgarian maternal genetic pool particularly suggests a major Western Eurasian origin, tracing their ancestry to lineages that witness a complex genetic structure of the region today and reflect different peopling and admixture events from the Upper Paleolithic to the onset of the Neolithic and Post-Neolithic in Europe15. Recent genome-wide ancient DNA (aDNA) based studies on Southeastern Europe, have shown that Neolithic population from present-day Bulgaria was closely related with the northwestern-Anatolian-Neolithic ancestry that signals the spread of Early farmers across Europe, except for the individuals lived in the mid-sixth millennium BC in Malak Preslavets, who revealed a significantly higher level of hunter-gatherer-related ancestry than the other Balkan Neolithic individuals18. Starting from the early 3rd millennium BCE, migrations from the adjacent Pontic-Caspian and Eurasian steppe also played an important role in the transformation of the European genetic landscape, and the contribution of Steppe ancestry to Southeastern European populations increased particularly during the Bronze Age18. Although our understanding of the population and cultural dynamics occurred in the (pre-) history of Balkan Peninsula is starting to be increasingly elucidated, the genetic details on the local civilization remain unknown and this information is only partly available for the ancient (proto-) Bulgarian people18,19. We now have the opportunity to investigate the genetic structure of the Thracians, an ancient people that lasted for more than five millennia and whose origin and relationships with other past and present-day populations are still debated among researchers.
To investigate the genetic structure and population history of this ancient civilization, we analyzed 25 complete mitochondrial genomes from three Thracian necropolises (Fig. 1 and Table 1) along with modern and ancient European data. The characterization of the Thracian mitochondrial DNA (mtDNA) variability may have important implications for understanding the dynamics of interaction between Eastern Europe and the Mediterranean, and will also contribute to better clarify the genetic evolution of European populations and the origin of contemporary Bulgarian gene pool.