Ancient genomes connect large-scale migration with the spread of Slavs

The second half of the first millennium CE in Central and Eastern Europe was accompanied by fundamental cultural and political transformations. This period of change is commonly associated with the appearance of the Slavs, which is attested by textual evidence1,2 and coincides with the emergence of similar archaeological horizons3–6. However, there is so far no consensus as to whether this archaeological horizon spread by migration, Slavicisation or a combination of both. Genetic data remains sparse, especially due to wide-spread practice of cremation in the early phase of the Slavic settlement. Here we present genome-wide data from 555 ancient individuals, including 359 samples from Slavic contexts dating as early as the 7th century CE. Our data demonstrates large-scale population movement from Eastern Europe during the 6th to 8th century, replacing over 80% of the local gene pool in Eastern Germany, Poland and Croatia. Yet, we also show substantial regional heterogeneity as well as a lack of sex-biased admixture, indicating varying degrees of cultural assimilation of the autochthonous populations. Comparing archaeological and genetic evidence, we find that the change in ancestry in Eastern Germany coincided with a change in social organization, characterized by an intensification of inter- and intra-site genetic relatedness and patrilocality. On the European scale, it appears plausible that the changes in material culture and language between the 6th and 8th centuries were connected to these large-scale population movements.