rare variants at 0.5% were observed in a single population (Fig. 2b). Within ancestry groups, common variants are weakly differentiated (most within-group estimates of FST are < 1%; Table S11), although below 0.5% frequency variants are up to twice as likely to be found within the same population compared to random sample from the ancestry group (Fig. S6a). The degree of rare-variant differentiation varies between populations. For example, within Europe, the IBS and FIN populations carry excesses of rare variants (Fig. S6b), which can arise through events such as recent bottlenecks10, ‘clan’ breeding structures11 and admixture with diverged populations12.
