This paper shows that Basques, who are viewed by some as a relatively isolated remnant of the European Paleolithic population, do not in fact show any signs of being a genetic isolate, having similar levels of heterozygosity, i.e., tendency to have different alleles in any particular locus, and linkage disequilibrium, i.e, the tendency of alleles in big blocks of DNA to be inherited together.
The MDS plot of the Fst distances is also quite interesting, showing Catalans, Extremadura, Basques, and Andalusians on the left, and Moroccans and Saharans on the right. As the authors note:
The MDS plot shows that genetic variation can be described with a single component, namely, Iberian vs North African populations (note the huge difference in scale between components 1 and 2), and Basques are not differentiated from other Iberian populations.
European Journal of Human Genetics doi:10.1038/ejhg.2009.69
Isolated populations as treasure troves in genetic epidemiology: the case of the Basques
Paolo Garagnani et al.
The Basques are a culturally isolated population, living across the western border between France and Spain and speaking a non-Indo-European language. They show outlier allele frequencies in the ABO, RH, and HLA loci. To test whether Basques are a genetic isolate with the features that would make them good candidates in genetic association studies, we genotyped 123 SNPs in a 1-Mb region in chromosome 22 in Basque samples from France and Spain, as well as in samples from northern and southern Spain, and in three North African samples. Both Basque samples showed similar levels of heterozygosity to the other populations, and the decay of linkage disequilibrium with physical distance was not different between Basques and non-Basques. Thus, Basques do not show the genetic properties expected in population isolates.