Laura Winkelbach

The emergence of new political and social structures in Western and Central Europe during the transition from Antiquity to the Middle Ages has long been attributed to large-scale migrations. Yet emerging evidence increasingly emphasizes the role of small-group mobility in reshaping the Roman world ^1–3 . Here we present 258 ancient genomes from the former Roman frontier of southern Germany, which we analyse alongside 2,500 ancient and 379 modern genomes. Population genetic analyses reveal a major demographic shift coinciding with the late fifth century collapse of Roman state structures, when a founding population of northern European ancestry mixed with genetically diverse Roman provincial groups. Pedigree reconstruction and filia, a method for inferring the ancestry of unsampled relatives, indicate widespread intermarriage and minimal cultural differentiation. Genetic structure persisted through the sixth century, with admixture forming a population resembling modern Central Europeans by the early seventh century. Using Chronograph to refine the chronology of genealogically linked individuals, we estimate a generation time of 28 years, life expectancies of 39.8 years for women and 43.3 years for men, high infant mortality, and a society in which nearly one quarter of children lost at least one parent by age 10, yet most still grew up with grandparents. Pedigrees further reveal a society centred on nuclear families that practiced lifelong monogamy, strict incest avoidance, flexible lineage continuation and no levirate unions, indicating continuity with Late Roman social practices that later shaped the European family.

Summary: Many European towns and villages trace their origins to Early Medieval foundations. In former Roman territories, their emergence has traditionally been linked to mass migrations from outside the Roman Empire. However, recent studies have emphasised local continuity with some individual-level mobility. We generated and analysed 248 historic genomes from Late Roman (3rd and 4th century CE) and Early Medieval (5th–8th century CE) burial sites in southern Germany, comparing them to over 2,500 contemporary and Iron Age genomes in addition to 1,344 modern-day genomes from Germany, Italy and Great-Britain. Despite small inferred Early Medieval period community sizes, genetic diversity exceeded that of modern German cities. In the Altheim graveyard, established in the 5th century by a group of Northern European descent, we inferred a demographic shift in the 6th century with the integration of newcomers with ancestry typical of a nearby Roman military camp, likely as a result of the collapse of Roman state structures. We reconstructed multigenerational pedigrees and, using a novel approach to infer ancestry of unsampled relatives, inferred immediate intermarriage between incoming and local groups, with a distinct tendency for men from former Roman background marrying women of northern descent. Burial proximity correlates strongly with kinship, in some cases spanning six generations. These communities were organized around small family units, exhibited loosely patrilineal or bilateral descent patterns, practiced reproductive monogamy, and avoided close-kin marriages. Such practices reflect broader transformations in family structures that began during the Late Roman period, were transferred to small agrarian societies in the Early Medieval period, and continued to shape European societies. By the 7th century, ongoing admixture had shaped genetic diversity patterns into those resembling Central Europe today.

Our understanding of prehistoric societal organization at the family level is still limited. Here, we generated genome data from 32 individuals from an approximately 3,800-y-old burial mound attributed to the Bronze Age Srubnaya-Alakul cultural tradition at the site of Nepluyevsky, located in the Southern Ural region of Central Eurasia. We found that life expectancy was generally very low, with adult males living on average 8 y longer than females. A total of 35 first-degree, 40 second-degree, and 48 third-degree biological relationships connected 23 of the studied individuals, allowing us to propose a family tree spanning three generations with six brothers at its center. The oldest of these brothers had eight children with two women and the most children overall, whereas the other relationships were monogamous. Notably, related female children above the age of five were completely absent from the site, and adult females were more genetically diverse than males. These results suggest that biological relationships between male siblings played a structural role in society and that descent group membership was based on patrilineality. Women originated from a larger mating network and moved to join the men, with whom they were buried. Finally, the oldest brother likely held a higher social position, which was expressed in terms of fertility.