A newly elaborated method, "Wombling," for detecting regions of abrupt change in biological variables was applied to 63 human allele frequencies in Europe. Of the 33 gene-frequency boundaries discovered in this way, 31 are coincident with linguistic boundaries marking contiguous regions of different language families, languages, or dialects. The remaining two boundaries (through Iceland and Greece) separate descendants of different ethnic or geographical provenance but lack modern linguistic correlates. These findings support a model of genetic differentiation in Europe in which the genetic structure of the population is determined mainly by gene flow and admixture, rather than by adaptation to varying environmental conditions. Of the 33 boundaries, 27 reflect diverse population origins at often distant locations. Language affiliation of European populations plays a major role in maintaining and probably causing genetic differences.
