| This study examines the position of the Basques in the genetic landscape of Europe using molecular genetic systems. Biparental markers (autosomal STRs and classical genetic markers) and uniparental markers (mtDNA haplogroups and HVS-I sequences, as well as Y-chromosome STR haplotypes) are used to address the origin and structure of the Basque population of Spain, as well as their role in the peopling of Europe. Three hypotheses of Basque origins are tested: (1) The Basques share a recent common ancestor with populations of the Caucasus; (2) The Basques are descendants of ancient Iberian populations who migrated from North Africa during the Neolithic; and (3) The Basques are a remnant population, the descendants of Paleolithic Europeans, who evolved in situ, with little gene flow from Neolithic farmers. The question of heterogeneity within the Basque population is addressed, and uniparental markers are examined for evidence of Neolithic ancestry in the Basque Provinces. Analysis of the molecular systems does not support a recent common ancestor between the Basques and populations either from the Caucasus or North Africa. While analysis of classical markers reveals the effects of genetic drift on the Basque population as a whole, AMOVA analysis of molecular markers demonstrates genetic homogeneity and little genetic structure between provinces (autosomal STRs: Va = -0.095, FCT = -0.0036, p = 0.878; Y-STRs: 1.71%, p = 0.0369; HVS-I sequences: 1.03%, &phgr; ST = 0.0103, p = 0.0308). In addition, heterozygosity versus rii of autosomal STRs reveals that the impact of genetic drift is mediated by the influence of gene flow in three of the Basque Provinces. Gene and haplotype diversity levels in the Basque population are on the low end of the European distribution (autosomal STRs: 0.0805, Y-STRs: 0.9421, mtDNA: 0.0114), but other European populations have equivalent or lower levels. Distribution of uniparental haplogroups demonstrates varying levels of Neolithic admixture in the Basque population, with both Neolithic maternal lineages (J) and paternal lineages (E1b1b, G2, J2a) present. While these results do not suggest that the ancient Basque population had direct contact with Neolithic farmers, the presence of these markers cautions against using the Basques as a proxy Paleolithic population in genetic studies. However, the Basques do have high frequencies of other uniparental haplogroups considered to be of Paleolithic origin (Y-chromosome: R1b, mtDNA: H, U5), and analysis of demographic processes using HVS-I sequences places the date of population expansion among the Basques squarely in the Paleolithic, arguing against the complete replacement demic diffusion model of the Neolithic transition. |
