Ancient genomes provide evidence of demographic shift to Slavic-associated groups in Moravia

The Slavs are a major ethnolinguistic group of Europe, yet the process that led to their formation remains disputed. As of the sixth century CE, people supposedly belonging to the Slavs populated the space between the Avar Khaganate in the Carpathian Basin, the Merovingian Frankish Empire to the West and the Balkan Peninsula to the South. Proposed theories to explain those events are, however, conceptually incompatible, as some invoke major population movements while others stress the continuity of local populations. We report high-quality genomic data of 18 individuals from two nearby burial sites in South Moravia that span from the fifth to the tenth century CE, during which the region became the core of the ninth century Slavic principality. In contrast to existing data, the individuals reported here can be directly connected to an Early-Slavic-associated culture and include the earliest known inhumation associated with any such culture. The data indicates a strong genetic shift incompatible with local continuity between the fifth and seventh century, supporting the notion that the Slavic expansion in South Moravia was driven by population movement.