Genetic structure of human populations in the British Isles.

Spatial patterns were studied for 36 allele frequencies representing 14 genetic systems (blood antigens, enzymes and serum proteins) in the United Kingdom and Irish Republic. The total number of data points over all systems and localities is 331. Patterns of genetic variation in space are graphically represented by one-dimensional and directional correlograms, and by interpolated allele-frequency surfaces. The data surfaces were examined by the various techniques of spatial autocorrelation analysis. Zones of rapid change across allele surfaces were discovered by the wombling method. Six allele frequency surfaces from four genetic systems exhibit significant spatial patterns. Only one pattern (IO; in the ABO system) may be described as purely clinal in an east-west direction; another (IB; in ABO) approximates a cline or at least north-south differentiation. A method was developed for testing the direction of maximal genetic autocorrelation. Two previously unrecorded patterns for the British Isles, north-south gradients for Rhesus and P, were detected. Twelve zones of rapid genetic change were discovered; some of these seem to reflect maritime and montane physical barriers as well as long-held cultural and linguistic differences, particularly between early Germanic and Celtic speakers. Moreover, some appear to reflect past historic events such as the invasions of Anglo-Saxons and Anglo-Normans.