Great Bolgar’s historical genetics: a genomic study of individuals from burials close to the Greek Chamber in the 14th century

Bolgar was one of the most significant mediaeval cities in Eastern Europe. Before the Mongol conquest, it served as a major administrative centre of Volga Bulgaria, and after 1236, it temporarily functioned as the capital of the Golden Horde. Historical, archaeological, and paleoanthropological evidence indicates a mixed population of this city during the 13th–15th centuries; however, the contributions of exact ethnic groups into its genetic structure remain unclear. To date, there are no genetic data for this medieval group. For the first time, using massive parallel sequencing methods, we determined whole-genome sequences for three individuals from Bolgar who were buried in the early 14th century close to the so-called “Greek Chamber”. The average coverage of the studied genomes ranged from x0.5 to x1.5. We identified the genetic sex of the people (two men and one woman), and performed a population genetic analysis. The authenticity of the DNA studied and the low level of contamination were confirmed, and the mitochondrial DNA haplogroups of all three individuals as well as the Y-chromosome haplogroups of two male individuals were determined. We used more than 2.7 thousand DNA samples from re presentatives of ancient and modern populations that had been previously published to perform a comparative population-genetic analysis. Whole-genome data analysis employing uniparental markers (mitochondrial DNA and Y chromosome) and autosomal markers revealed genetic heterogeneity in this population. Based on PCA and f4 - statistics analysis, a genetic connection was identified between one of the individuals (female) and modern Finno-Ugric peoples of the Volga-Ural region. Genomic analysis of the other two individuals suggests their Armenian origin and indicates migrant influx from the Caucasus or Anatolia. The results align well with archaeological and paleoanthropological findings and significantly enhance them by reconstructing the contributions of the indigenous population to the formation of the mediaeval Bolgar population structure.