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Ancient DNA Sequences Inform Southern Arc History, Population Dynamics

NEW YORK – A set of ancient DNA analyses published on Thursday have started teasing apart the population history of a southern European/Western Asian region known as the Southern Arc.

Investigators from Harvard University, the Broad Institute, the University of Vienna, and elsewhere considered new sequence data for 777 individuals found in the region — sometimes called the "cradle of Western civilization" — spanning some 10,000 years, from the Neolithic to Ottoman periods.

The datasets, presented in three studies appearing in Science, included 727 newly sequenced samples, along with new sequence data for 50 samples considered in the past. Together with available archaeological insights, the genetic findings made it possible to trace population migrations and interactions with local hunter-gatherer and farming groups in the region over time.

"Our newly reported data fill many sampling gaps in space and time in the Southern Arc," senior authors David Reich, a human evolutionary biology and genetics researcher at Harvard, and Ron Pinhasi, an evolutionary anthropology and human evolution and archaeological sciences researcher with the University of Vienna, and their colleagues wrote.

For the first of these studies, the team turned to sequencing to characterize genome-wide variant patterns in Chalcolithic and Bronze Age samples going back 3,000 to more than 7,000 years. The work not only underscored the significant genetic interactions that took place between the Southern Arc and Eurasian Steppe at that time, they explained, but also provided a look at the interplay between human population dynamics and linguistic changes.

In particular, the investigators explored the roots of Indo-European languages such as Greek, using genetic patterns and archaeological clues to link these languages to Yamnaya culture steppe pastoralists.

Along with migrations north to the steppe and west through Anatolia by groups from the Caucasus, for example, the team's results suggested that Yamnaya individuals migrated northwest to present-day Europe, east to Eastern Europe, China, and India, and south into the Balkans, Greece, and Armenia in the Caucasus.

"Anatolia was transformed by intra-West Asian gene flow, with negligible impact of the later Yamnaya migrations," the authors noted. "This contrasts with all other regions where Indo-European languages were spoken, suggesting that the homeland of the Indo-Anatolian language family was West Asia, with only secondary dispersals of non-Anatolian Indo-Europeans from the steppe."

The researchers performed more in-depth analyses on each of the regions contributing to the interactions and migrations identified, while digging into Y chromosome data to retrace male-specific population patterns in the Southern Arc and beyond.

For another study in Science, members of the same team tracked population movements into and within Mesopotamia and Anatolia during "Pre-Pottery" and "Pottery" points of the Neolithic period.

Among other results, the investigators saw Anatolian, Caucasus, and Levantine hunter-gatherer ancestry in Pre-Pottery Neolithic individuals in and around the area that is now northern Iraq, southeastern Turkey, Cyprus, the Zagros Mountains, and Armenia. In Anatolia, meanwhile, they teased out the distinct population and admixture patterns found in the Pre-Pottery and Pottery points in the Neolithic.

"By analyzing Pre-Pottery and Pottery Neolithic populations of Anatolia, we show that the former were derived from admixture between Mesopotamian-related and local Epipaleolithic-related sources," the authors reported, "but the latter experienced additional Levantine-related gene flow, thus documenting at least two pulses of migration from the Fertile Crescent heartland to the early farmers of Anatolia."

Finally, for a third paper, the researchers considered more recent populations in the Southern Arc region, stretching into recorded history in West Asia and Southern Europe, retracing population patterns and movements related to the Mycenean period, Urartian Kingdom, and Roman Empire reaching into Medieval times.

"The works of ancient writers provide powerful insights into the ancient world, recording information on different groups, their political organization, customs, relations, and military conflicts. The manuscript tradition has been augmented by the archeological record, which also includes the discovery texts of past Mediterranean and West Asian civilizations," the authors explained, noting that "we leverage the power of ancient DNA to provide a third source of information about the people inhabiting the states and empires of the past."

That study also included genetics-informed predictions related to phenotypes such as eye or skin color.

For their part, the authors suggested that "malleability of human phenotypes across time and the presence of diverse ones — whether dark, light, or intermediate — across space undermine prejudiced views of history that overemphasize superficial traits at the expense of more meaningful aspects of human culture and biology."

In a corresponding perspectives article in Science, University of North Carolina at Chapel Hill anthropology researcher Benjamin Arbuckle and UNC at Chapel Hill's Zoe Schwandt noted that the studies "represent an important milestone for ancient genomic research, providing a rich dataset and diverse observations that will drive the next iteration of interpretations of the human history of West Eurasia."

Even so, they urged care around phenotypic analyses done with ancient DNA and cautioned that the interpretation of large datasets generated in such locations "represents worldviews that center certain people and places."