Unveiling the complexity of post-Roman polity formation in Pannonia using ancient DNA

: The transformation of the Roman world [fourth to ninth centuries common era (CE)], culminating in the Western Roman Empire's fall, marked a fundamental transition in European history. Key questions persist regarding the regionally specific nature of this transformation. We generated a paleogenomic dataset to reconstruct post-Roman organizations in the Little Hungarian Plain at microregional resolution. Genetic and archaeological analyses of two Roman (n = 68) and five post-Roman (n = 246) sites reveal a rise in Northern European ancestry, reflecting large-scale population movements into this region. Moreover, despite post-Roman sites sharing similar genetic profiles, material culture, and burial practices, they show distinct social structures, especially regarding the role played by biological relatedness. These findings highlight local hierarchies and reveal the making of a post-Roman polity.