Ancient DNA reveals reproductive barrier despite shared Avar-period culture

After a long-distance migration from the East, Avar people of Eastern Asian ancestry arrived in Eastern Central Europe in 567/568 CE and encountered groups with very different, European ancestry1,2. We used ancient genome-wide data of 722 individuals and fine-grained interdisciplinary analysis of large 7th-8th c. CE neighboring cemeteries south of Vienna (Austria) to address the centuries-long impact of this encounter1,2. We found that the ancestry at one site (Leobersdorf) was and remained dominantly East-Asian-like, even 200 years after the Avar immigration, while the other site (Mödling) displays local, European-like ancestry. These two nearby sites exhibit very few links of direct biological relatedness, despite sharing a distinctive late-Avar culture3,4. We reconstructed 6-generation pedigrees at both sites linking together up to 450 closely-related individuals, allowing per-generation demographic profiling of the communities. Despite different ancestry, these pedigrees together with large networks of distant relatedness display an absence of consanguinity, a strong patrilineal pattern with female exogamy, multiple reproductive partnerships (e.g. levirate) and direct correlation of social status to biological connectivity through markers of high social status in the archaeological material. The generation-long genetic barrier was maintained by systematically choosing partners with similar ancestry from other sites in the Avar realm. Leobersdorf had more biological connections with the Avar heartlands than Mödling, which is instead linked to another site from the Vienna Basin with European-like ancestry. Mobility between sites was mostly due to female exogamy pointing to different marriage networks as the main driver of the maintenance of the genetic barrier.