The expansion of the Slavs is one of the most important, yet still not fully understood, events in European history. From the 6th century AD onwards, reports of Slavic groups inhabiting vast territories - from the Baltic to the Balkans and from the Elbe to the Volga - appear in Eastern and Western European sources. However, unlike the better-described campaigns of the Goths, Langobards or Huns, the "origins" of the Slavs have long remained shrouded in mystery.

"One reason for this is that the first Slavic communities left behind only a few material, archaeological monuments. They burned their dead, built only simple dwellings and produced moderately decorated pottery. No writing was produced or preserved, and on that account, records directly from the Slavs only appear centuries after their supposed arrival. The very term "Slavs" can be ambiguous, as it comes from foreign sources, not from the Slavs themselves, and in later times was often misused for ideological purposes. The questions of where the Slavs came from and how they were able to fundamentally transform the cultural and linguistic map of Europe have remained unanswered and have been the subject of much debate," explains Zuzana Hofmanová, one of the principal authors of the two new studies, from the Department of Archaeology and Museology at the FF MU and the Max Planck Institute in Leipzig.

For decades, historians have debated whether Slavic culture and language spread through mass migration, the gradual "Slavization" of the local population, or a combination of both processes. However, convincing evidence has long been lacking.

An international team of scientists from Germany, Austria, Poland and Croatia, with a decisive representation of scientists from Masaryk University, has now developed the first comprehensive continental study of the ancient DNA of medieval Slavic populations. New scientific methods that were not available just a few years ago have made this possible. Genetic analyses of more than 500 human remains dated back to the first millennium AD have confirmed the widespread impact of migratory movements, regional diversity and new insights into the organisation of early medieval communities. Genetic analysis has shown that from the 6th century AD onwards, migrations of these Eastern European populations occurred across Central and Eastern Europe, fundamentally changing the genetic composition of regions, including the present-day territory of our country. However, this was not a conquest model. Instead of armies and elite structures, migrants built new societies based on extended families and flexible communities.

New studies, one of which is published today in the journal Nature, don't just answer how one of the world's largest language groups came to be. It also offers new insights into why the Slavs have been so successful. It was probably because they were not just elites, but entire communities. "The Slavs may have succeeded precisely because they eschewed the rigid structures of the Roman world. Their simple lifestyle and social flexibility allowed them to thrive in times of instability. New genetic data confirms this picture: same origins, varying degrees of mixing with local groups. In the north, the indigenous population is disappearing, and in the south, it is more likely to mix. This mosaic explains the genetic and cultural diversity of today's Europe," says Jiří Macháček, head of the Department of Archaeology and Museology at the FF MU, who is the guarantor of the four-year RES-HUM project (Ready for the Future: Understanding the Long-term Resilience of Human Culture), which helped fund the studies.

According to the researchers, the Slavic expansion may be the last major demographic event that has permanently and fundamentally changed Europe's genetic and linguistic map. "With these new results, we can look beyond the written sources and reconstruct the true extent of Slavic migration - one of the most influential yet least appreciated chapters of Europe's past," Hofmanová adds.

Genetic clues point to Slavic origins in the area between southern Belarus and central Ukraine, which is consistent with long-supposed linguistic and archaeological hypotheses. Although direct evidence from early Slavic core areas is still scarce, these genetic data provide the first concrete clues - the most likely origin is between the Dniester and the Don.

From the 6th century AD onwards, there were large-scale migrations of this eastern European population across central and eastern Europe, fundamentally changing the genetic composition of regions such as eastern Germany and Poland. However, the course of change has varied in the different areas. In eastern Germany, large family lines emerge, contrasting with the small families of the earlier period. In Croatia, on the other hand, migrants merge more with the original inhabitants, and the social structure changes only slightly. This regional diversity shows that the spread of the Slavs was not a uniform process but a mosaic of adaptations to local conditions.

"Slavic expansion was not one homogeneous movement but a collection of different migration stories - and there was no single 'Slavic identity'. Fundamentally, there is no evidence in the genetic data of a majority migration of one sex: whole families migrated, men and women, and together they formed new societies. Future research will show how such individual communities continued to adapt, integrate, or change completely as a result of migration and their own evolution," Hofmanová explains.

A separate study published in the journal Genome Biology showed a population change also in southern Moravia. "There was clear genetic evidence of a demographic change related to the transition to Slavic material culture, which originated in present-day Ukraine," says Denisa Zlámalová from Masaryk University, one of the study's authors. "The DNA analyses included a child buried in an early Slavic context, typically associated only with cremation," explains archaeologist Jiří Macháček, one of the study's authors. This finding is regionally and temporally linked to a culture with Prague-type pottery. The same genetic signal appears in individuals from the 9th-10th centuries, i.e. also during the time of the Moravian Principality known thanks to St. Cyril and Methodius and the emergence of Old Slavonic and Glagolitic during their arrival and the spread of Christianity in Moravia.

The research was supported and funded by the Swiss National Science Foundation, the Grant Agency of the Czech Republic (FORMOR project), the European Research Council (ERC Synergy Grant HistoGenes) and the OP-JAK RES-HUM project.