Pre-Slavic and Slavic Interaction at Eastern Periphery of Slavic Expansion in Northeastern Europe (Y-Gene Pools of Volga-Oka Region)

<b>Background/Objectives</b>: The eastern periphery of the Slavic expansion (the Volga-Oka region) is the most promising region for reconstructing interactions between Slavic and pre-Slavic populations of the East European Plain. Unlike most pre-Slavic tribes, its autochthonous population practiced inhumation instead of cremation, leaving us with some ancient DNA for analysis. <b>Methods</b>: The region's modern and ancient Y-chromosome gene pools are dominated by the haplogroup R1a: its frequency reaches 56% in Ryazan Russians (n = 302) and 44% in the Finnic peoples of Mordovia (n = 633). This encouraged us to analyze its Y-SNPs and Y-STRs. <b>Results</b>: Using 2 independent methods of phylogeny analysis, we identified 10 informative Y-STR clusters within R1a, dating back 1600-2900 YBP. The clusters included 48% of modern Ryazan Russians, 40% of Mordovia's Finnic populations, and ancient DNA samples from the Ryazan-Oka culture (6-7th centuries), Suzdal (12-13th centuries) and Vladimir (13th century). Such a unique combination and pre-Slavic TMRCA indicate that the informative clusters represent pre-Slavic Y lineages. The presence of ancient samples from Vladimir and Suzdal in the clusters suggests that the autochthonous tribes contributed to shaping the urban population of the Vladimir-Suzdal Rus. Some of the informative clusters are associated with the ancient population of the Baltics (2000-4000 YBP). <b>Conclusions</b>: About half of Russian R1a carriers in the Volga-Oka region are descended from a pre-Slavic population, suggesting that the Slavs did not fully replace the autochthonous population but rather mostly culturally assimilated the Meshchyora documented in the Russian chronicles and other local tribes.