Archaeogenetic characterization reveals social endogamy among Samnite groups in ancient pre-Roman Italy (Pontecagnano, Campania, 5th-4th century BCE)

The Samnites, prominent competitors of the Romans prior their dominance over the Italian peninsula in the 3rd century BCE, underwent a transformative cultural period known as the ‘Samnitization process’ between the 5th and 4th centuries BCE. This marked a shift in the political structure of Italic populations, involving mobility of groups from inland central Italy to the Campania region in the south. While the analysis of topography, spatial organization, and material culture has shed light on these migrations, biosocial and biocultural aspects of this process remain largely unexplored. In this study, we integrated osteological and archaeological data with new genomic data obtained from the disarticulated petrous bones of 26 individuals inhumated in the funerary sector of Di Renna (5th–4th centuries BCE) within the eastern necropolis of the Etruscan-Campanian site of Pontecagnano (Salerno, southern Italy). The archaeological interpretation based on the grave goods allowed us to identify individuals belonging to Samnite groups; ‘aeroplano’ fibula was usually found in female and non-adult burials while males were adorned with bronze belt and spear. As for topography of Di Renna funerary sector, several family clusters were identified. Biocultural relatedness was supported by characterization of genetic kinship and detection of runs of homozygosity providing direct evidence of consanguineous marriage practices among cousins at high frequencies during 425-375 BCE, the later phase of the Samnitization. Genomic data also revealed that the ancestry of these individuals mainly arose from the Italian mainland, with some showing additional ancestry from the eastern Mediterranean. Our results shed light on the social organization of this ancient group and highlight the potential of archaeogenetic approaches for unravelling the inter- play of genetic admixture, mating patterns, and marital practices associated to mobility in pre-Roman Italy.