Genetic continuity of Bronze Age Ancestry with increased Steppe-related ancestry in the Late Iron Age Uzbekistan

While a well-studied Bronze Age civilization, Bactria-Margiana Complex (BMAC), is an important part of ancient Uzbekistan and Central Asia, the Iron Age was also a dynamic period that resulted in increased interaction and admixture among the different cultures from this region. To broaden our understanding of how events following the Bronze Age impacted the regional demography and population structure of this region, we generated 27 genome-wide SNP capture datasets of Late Iron Age individuals (~2100-1900 BP) from three sites in South Uzbekistan. Overall, Bronze Age ancestry persists into the Iron Age in Uzbekistan, with no major replacements of populations with Steppe-related ancestry. However, these individuals suggest diverse ancestries comprising Iranian farmers, Anatolian farmers and Steppe herders, with small amount of West European Hunter Gatherer and East Asian ancestry. Genetic affinity towards the Late Bronze Age Steppe herders and a higher Steppe-related ancestry than that found in BMAC populations suggest an increased mobility and interaction of individuals from the Northern Steppe in a southward direction. In addition, a decrease of Iranian farmer-like and an increase of Anatolian farmer-like ancestry in Uzbekistan Iron Age individuals were observed compared to the BMAC populations from Uzbekistan. Thus, despite continuity from the Bronze Age, increased admixture played a major role in the shift from the Bronze to the Iron Age in southern Uzbekistan. This mixed ancestry is also observed in other parts of the Steppe and Central Asia, suggesting more widespread admixture among local populations.