Consanguinity and Social Structure in the Roman World: A Diachronic Genomic Analysis

Abstract

This study investigates the diachronic alteration of consanguinity from the Iron Age to the Early Middle Ages across Anatolia, the Balkans, and Southern Europe. To achieve this, I introduce a novel probabilistic framework, ROHClassifier, to distinguish parental kinship degrees based on Runs of Homozygosity (ROH), enabling a high-resolution reconstruction of mating patterns from ancient genomes. The analysis of the compiled genomic dataset reveals starkly divergent regional trajectories under Roman rule. While the Italian Peninsula experienced a dramatic exogamic shift—marked by a significant reduction in consanguinity during the Imperial period—the eastern provinces demonstrated profound structural continuity. In Anatolia and the Balkans, highly endogamous mating networks proved remarkably resilient, a continuity shown to be deeply anchored in rural contexts such as the Imperial-era homestead at Nevali Çori. Beyond these macro-scale baselines, micro-historical analyses of extreme biological outliers illuminate how society managed profound taboos. The offspring of full-sibling incest interred in a Nicaean infant trench (I14844) provides compelling evidence for institutional care (brephotrophia) in Late Antiquity, while a burial at the Viminacium frontier (R6750) reflects the complex ritual inclusion of marginalized individuals. Ultimately, these findings demonstrate that biological kinship was an active social strategy, revealing how Eastern Mediterranean communities successfully buffered their intimate family structures against the universalizing forces of the Roman Empire.