Imputed genomes and haplotype-based analyses of the Picts of early medieval Scotland reveal fine-scale relatedness between Iron Age, early medieval and the modern people of the UK

The Picts were a tribal confederation of peoples living in what is now eastern and northern Scotland during the Late British Iron Age and Early Medieval periods. Despite being instrumental in preventing the northward expansion of the Roman Empire in Britain, much about Pictish culture and history, including their genetic affinities and population structure, remains enigmatic. Here we present genomic evidence from 23 individuals associated with Pictish burial sites, analysed alongside >8,300 previously published ancient individuals and >16,500 present-day reference samples. Using novel haplotype-based approaches, we demonstrate local genetic continuity spanning the Iron Age transition and identify broad genetic affinities between the Picts and Iron Age peoples across Britain. We observe a high degree of local genetic continuity from the Iron Age (∼2,000 BP) through to the present in Scotland, and show that the Picts were genetically 'unremarkable' in the context of the pre-existing Iron Age gene pool of the British Isles. In addition, we demonstrate a striking degree of fine-scale population structure and inter-individual relatedness within geographically restricted areas. This suggests that the Pictish territories were composed of close-knit communities with limited gene flow over large distances, and that much of the genetic diversity observed in the British Isles today was likely established prior to the Pictish period.