TEHRAN - The Zagros mountain range and its foothills have long served as a crossroads for the movement of peoples, cultures, and languages. A question that has occupied scholars for decades is whether these cultural influences and population movements were accompanied by significant genetic changes. New research published in Genome Biology, which analyzed the ancient DNA of 17 individuals from the archaeological site of Bakr Awa in Iraqi Kurdistan, located in the western foothills of the Zagros, offers important insights into this question.

Bakr Awa is one of the largest archaeological mounds in Iraqi Kurdistan, situated near the Iranian border. Located in the Shahrizor Plain close to the city of Halabja, its strategic position made it a key corridor for trade and communication between the Zagros foothills, the highland communities of the Zagros Mountains, and populations farther east on the Iranian Plateau. Archaeological excavations have revealed cultural influences from southern Mesopotamia, Anatolia, and the Caucasus. But was this cultural diversity also reflected in the genetic makeup of its inhabitants?

By extracting DNA from human remains dating to the Bronze Age (ca. 4000–1200 BCE) and the Iron Age (1200–550 BCE), researchers reconstructed a remarkable picture of the region’s population history. Their findings reveal that during the Bronze Age, Bakr Awa was home to a highly diverse population. Rather than descending from a single ancestral group, the inhabitants were the product of admixture among populations with Anatolian, Levantine, Caucasian, and Eurasian Steppe ancestry.

This genetic diversity stands in marked contrast to the population structure of the earlier Pre-Pottery Neolithic period in the same region. While individuals from the nearby Neolithic site of Bestansur show the strongest affinity to Neolithic populations from the central Zagros Mountains, the Bronze Age inhabitants of Bakr Awa represented a genetic mosaic of multiple ancestral groups. In simple terms, the demographic composition of the region underwent profound changes over the course of several millennia.

The significance of these findings extends beyond Iraqi Kurdistan. Bakr Awa and neighboring sites lie along the northwestern extension of the Zagros range—the same mountain system that stretches through western Iran. As a result, the demographic and genetic developments documented at Bakr Awa may offer valuable insights into parallel processes that occurred in the Iranian Zagros and could help guide future genetic investigations at archaeological sites in western Iran.

One particularly intriguing discovery was the identification of an Early Bronze Age adolescent who carried clear evidence of Caucasus-Steppe ancestry in both his genome and Y chromosome. Strontium and oxygen isotope analyses of his teeth indicated that he had recently migrated to Bakr Awa from the Zagros Mountains. This individual provides rare and direct evidence of human mobility during the second millennium BCE and highlights the close connections linking communities on both sides of the Zagros.

Perhaps the most significant finding of the study concerns the transition from the Bronze Age to the Iron Age. Bakr Awa was destroyed by a major fire during the Late Bronze Age, around the fifteenth to fourteenth centuries BCE, and was subsequently abandoned for a period. When the site was reoccupied during the Iron Age, an important question emerged: did this resettlement involve the arrival of a new population?

The genetic evidence suggests that it did not. The DNA of Iron Age inhabitants indicates that they were not newly arrived migrants or invaders but rather descendants of the same diverse Bronze Age population. In other words, the multiple genetic lineages present during the Bronze Age were not replaced by a new population during the Iron Age; instead, they became increasingly integrated over time. These findings challenge conventional assumptions about demographic change following the Late Bronze Age collapse and demonstrate that major cultural and political transformations do not necessarily coincide with large-scale population replacement.

Overall, the study reveals a dynamic demographic history in which the region was characterized by substantial genetic diversity during the Bronze Age, followed by increasing integration and admixture during the Iron Age. Conducted through a collaboration among researchers from universities in Australia, the United States, Poland, Germany, and the United Kingdom, this research underscores a broader lesson: human genetic history, much like cultural history, is shaped by continuous processes of migration, interaction, admixture, and transformation. The archaeological sites of western Iran will undoubtedly provide crucial evidence for future chapters of this unfolding story.

AM