Ancient DNA reveals matrilineal organisation and recurrent unions between dominant matrilines in Iron Age Britain.

Kinship practices underpin all traditional societies, forming the basis for socially sanctioned reproductive unions, residence patterns and the inheritance of rights and property 1,2 . Although the relationship between biological relatedness and kinship is not always straightforward, ancient DNA studies are increasingly used to examine the extent to which biological relatedness underpinned social constructs of kinship in prehistoric societies 3-6 . Here, we report the analysis of genome-wide data for 534 individuals from the Arras Culture of Middle Iron Age northeast England (including 390 from Wetwang Slack, 100 from Pocklington, and 29 from Melton), finding evidence for communities with kinship systems structured along matrilineal lines. At Wetwang Slack, we reconstruct a 13-generation pedigree comprising 195 individuals structured around female-line connections: matrilineal transmissions greatly outnumbered patrilineal ones and male reproductive partners were largely absent from the cemetery, plausibly because they were buried in their own natal communities. Furthermore, the three main sites with robust sample sizes were characterised by non-overlapping dominant mitochondrial haplogroups, implying a maternal clan-based structure. Reproductive unions at Wetwang Slack suggest a recurrent alliance between two dominant maternal descent groups, with members of each group never reproducing with members of their own maternal lineage. Meanwhile, three individuals from lavishly furnished 'chariot burials' at Wetwang Slack were close maternal relatives belonging to a lineage with consecutive generations of close kin unions, a pattern largely absent among other individuals at the site. These results indicate highly distinctive social practices among an elite group embedded in the wider kinship network of the Arras community.