Fine-scale genetic variation between human populations is interesting as a signature of historical demographic events and because of its potential for confounding disease studies. We use haplotype-based statistical methods to analyse genome-wide single nucleotide polymorphism (SNP) data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom. This reveals a rich and detailed pattern of genetic differentiation with remarkable concordance between genetic clusters and geography. The regional genetic differentiation and differing patterns of shared ancestry with 6,209 individuals from across Europe carry clear signals of historical demographic events. We estimate the genetic contribution to southeastern England from Anglo-Saxon migrations to be under half, and identify the regions not carrying genetic material from these migrations. We suggest significant pre-Roman but post-Mesolithic movement into southeastern England from continental Europe, and show that in non-Saxon parts of the United Kingdom, there exist genetically differentiated subgroups rather than a general ‘Celtic’ population. Extensive genetic analysis of over 2,000 individuals from different locations in Britain reveals striking fine-scale patterns of population structure; comparisons with similar genetic data from the European continent reveal the legacy of earlier population migrations and information about the ancestry of current populations in specific geographic regions. Genetic data have been used widely to inform our understanding of population history and migrations. Now with the advent of genome-wide analysis of single nucleotide polymorphism (SNP) data — cataloguing variation between individuals at a single position in the genome sequence — fine-scale genetic variation between human populations can be used as a signature of historical demographic events. Peter Donnelly and colleagues use such data from a selected geographically diverse sample of more than 2,000 individuals from the United Kingdom to reveal remarkable concordance between genetic clusters and geography. The results throw new light on several aspects of the peopling of Britain. For instance the genetic contribution to southeastern England from Anglo-Saxon migrations is under half, suggesting significant pre-Roman but post-Mesolithic population movement from the European continent. The data also reveal that non-Saxon regions contain genetically differentiated subgroups rather than a general 'Celtic' population.

The fine-scale genetic structure of the British population