Ancient Roman mitochondrial genomes and isotopes reveal relationships and geographic origins at the local and pan-Mediterranean scales

Rome initiated several campaigns to expand, conquer, and enslave local Italic populations following the establishment of the republic in 504 BCE. However, the cultural and biological changes resulting from Roman subjugation across Italy remain a topic of intense historical debate. Although important, historic and archaeological lines of evidence fail to track the impact of forced enslavement and enculturation at individual and broader genetic scales and, more generally, offer fewer clues regarding the potential affinities of Roman period Italians to European, Near Eastern, western Asian and North African populations at this time. In this paper, we present the whole mitochondrial (mtDNA) genomes of 30 Roman period (1st-4th centuries CE) individuals buried in the Vagnari necropolis in southern Italy. We integrate the mtDNA data with previously published bioarchaeological and isotope (delta O-18 and Sr-87/Sr-86) data for the Vagnari assemblage and compare Roman haplogroup composition to 15 newly sequenced mitochondrial genomes obtained from a pre-Roman Iron Age skeletal assemblage, located in close proximity to Vagnari. Additionally, we contrast our South Italian dataset with a further 332 complete ancient mtDNA genomes from the pan-Mediterranean region, Europe, western Asia and North African regions. Population pairwise Phi(ST) values suggest that Roman Italians share closer genetic similarity to Neolithic, Bronze Age, and Armenian Iron Age populations from western and central Eurasia than with Iron Age Italians, Ptolemaic, and Roman period Egyptians. Vagnari individuals with delta O-18 and Sr-87/Sr-86, and mtDNA data suggest a predominantly local demographic was employed at the site. However, two individuals belong to eastern Eurasian haplogroup D4b1c, indicating that the maternal ancestors of these two individuals migrated to South Italy prior to the 1st century CE. Additionally, we provide the first genetic evidence for possible maternal relatedness in a Roman period skeletal assemblage. Our research highlights the significance of integrating multiple lines of bioarchaeological data to inform interpretations about Roman colonial expansion and its impact on population structure.