Population-scale analysis of inheritance patterns across 858,635 individuals reveals recent historical migration patterns across the North Sea from the Middle Ages to the Industrial Revolution

This preprint analyzes haplotype (identity-by-descent) sharing among 858,635 contemporary individuals from Denmark and Britain to reconstruct migration history from the Middle Ages into the Industrial Revolution. The authors infer fine-scale population structure within Denmark using nationwide biobank data and validate inferred relationships against national registry pedigrees. They detect marked historical differences across Danish regions, including a late-medieval to early-modern population decline in Jutland and migration toward Zealand, consistent with historical records. Cross-North Sea analyses reveal two principal patterns between Denmark and Great Britain: (1) earlier coast-to-coast connections linking South Jutland and eastern England, likely reflecting Viking-era settlement and sustained trade and mobility through early modern times, and (2) later city-to-city links (e.g., London–Copenhagen) shaped by urbanization and shifts in economic hubs toward the Industrial Revolution. Comparisons involving other North Sea countries indicate both shared and region-specific histories of genetic exchange. The study highlights the power of population-scale modern genetic resources to illuminate recent historical migrations.