Personalized genealogical history inferred from biobank-scale IBD segments

When modern biobanks collect genotype information for a significant fraction of a population, dense genetic connections of a person can be traced using identity by descent (IBD) segments. These connections offer opportunities to characterize individuals in the context of the underlying populations. Here, we conducted an individual-centric analysis of IBDs among the UK Biobank participants that represent 0.7% of the UK population. On average, one UK individual shares IBDs over 5 cM with 14,000 UK Biobank participants, which we refer to as "cousins". Using these segments, approximately 80% of a persons genome can be reconstructed. Also, using changes of cousin counts sharing IBDs at different lengths, we identified a group, potentially British Jews, who has a distinct pattern of familial expansion history. Finally, using the enrichment of cousins in ones neighborhood, we identified regional variations of personal preference favoring living closer to ones extended families. In summary, our analysis revealed genetic makeup, personal genealogical history, and social behaviors at population scale, opening possibilities for further studies of individuals genetic connections in biobank data.