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DNA Reveals Roman Empire's Impact on Balkan Populations

This photograph shows a Roman aqueduct that supplied water to Viminacium, a large Roman city.
This photograph shows a Roman aqueduct that supplied water to Viminacium, a large Roman city. Credit: Carles Lalueza-Foz.
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Analyzing DNA extracted from ancient individuals or artifacts can help scientists understand the origins of early humans and how they inhabited our planet. When studied alongside historical and archaeological records, ancient DNA can also provide novel insights into more recent historical periods, including the age of the Roman Empire.

A collaborative team of scientists investigated the ancestry of people who occupied the Balkans during the rise and fall of the Roman Empire, using ancient DNA analysis. Their research is published in Cell.

The Balkans and the fall of the Roman Empire

The researchers analzyed DNA extracted from 136 individuals who inhabited 20 sites across the Balkans between during the first millenium CE. “This region was one of the distant frontiers of the Roman Empire, which makes it interesting to study because this is clearly a place where you would expect people to come in contact with people from outside the Empire, so you can test things such as globalization,” says Iñigo Olalde, a population geneticist at the University of the Basque Country (UPV/EHU), and the study’s first author.

The Balkans

The Balkans is a region in Southeast Europe that is also known as the Balkan Peninsula. Its name derives from the Balkan Mountains, which stretch from Bulgaria to Serbia. Several countries are considered to be part of the Balkans, including but not limited to Albania, Croatia, Greece, Slovenia and parts of Romania.

“Ancient DNA can give a lot of insight into historical periods, especially for regions where historical sources are scarce or when we don’t know whether sources are biased or not,” Olalde adds, emphasizing that many historical records from the Balkans are written from the perspective of the Romans, as Slavic people did not write at that point in history.

No genetic evidence of Iron Age Italian ancestry

Ancient DNA was analyzed from graves in large Roman cities, small towns and military fortresses. The researchers concentrated their analyses on three time periods: 1–250 CE, when the Roman empire was at its height, 250–550 CE – the late Imperial period – and 550–1000 CE, after the Western Empire had collapsed. In collaboration with local historians and archeologists, the researchers documented the burial type for each individual, in addition to any objects that were found in the grave. They also adopted radiocarbon dating to confirm the age of 38 individuals, producing isotopic data that could provide insight into their diets.

To their surprise, the researchers found little ancestry contribution from individuals of Italian descent in the Balkan populations during the Roman Empire’s height. “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,” they write. Rather, they disovered that people from Western Anatolia, another part of the Roman Empire, migrated to the Balkans during this period.

Genetic evidence of individuals migrating into the Balkans from within and outwith the Roman Empire was also uncovered. A 16-year-old male, excavated from a necropolis in a large Roman city, was found to be of East African ancestry. “The individual of East African ancestry was buried with an oil lamp depicting Jupiter-related eagle iconography, not a common finding in Viminacium graves,” the authors describe. “Isotopic analysis of tooth roots showed that he was also an outlier with respect to dietary habits during childhood, with elevated δ15N and δ13C values indicating the likely consumption of marine protein sources.”

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The male possibly spent his early years in East Africa, the researchers say: “Although we will never know his whole life story, whether as a 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.”

“This was the only full East African individual that we analyzed, and he was also a clear outlier with respect to the diet compared to the rest of the individuals buried in the same necropolis, which tells us that this individual clearly grew up outside the borders of the Roman Empire,” says senior author and paleogenomicist Professor Carles Lalueza-Fox from the Institute of Evolutionary Biology (IBE:CSIC-Universitat Pompeu Fabra) and Museu de Ciències Naturals de Barcelona.

Migrants of mixed ancestry frm Northern Europe and the Pontic-Kazakh steppe were identified during the late Imperial period. “We found that those two ancestries – central/northern European and Sarmatian-Scythian – tended to come together, which suggests that these are likely to have been multi-ethnic confederations of moving people,” says Professor David Reich, senior author and population geneticist at Harvard University.

The data implies an influx of individuals from Eastern Europe occurred shortly after the fall of the Western Roman Empire, as the remains sampled at this time possess similar ancestry to present-day Eastern European populations. “There have been debates about how impactful these migrations were and to what extent the spread of Slavic language was largely through cultural influences or movements of people, but our study shows that these migrations had a profound demographic effect,” says Reich. “More than half of the ancestry of most peoples in the Balkans today comes from the Slavic migrations, with around a third Slavic ancestry even in countries like Greece where no Slavic languages are spoken today.”

Ancient DNA sequencing techniques continue to advance, and the researchers plan to embrace these sophisticated techniques in another study. “We are now able to sequence hundreds of individuals from the same site, so we can go to another level of resolution and start to understand more about the social interactions and kinship between the different individuals,” Olalde concludes.

Reference: Olalde I, Carrión P, Mikic I, et al. A genetic history of the Balkans from Roman frontier to Slavic migrations. Cell. 2023. doi: 10.1016/j.cell.2023.10.018

This article is a rework of a press release issued by Cell Press. Material has been edited for length and content.