Summary

Genetic diversity in Europe has been interpreted as a reflection of phenomena occurring during the Paleolithic (»45,000 years before the present [BP]), Mesolithic (»18,000 years BP), and Neolithic (»10,000 years BP) periods. A crucial role of the Neolithic demographic transition is supported by the analysis of most nuclear loci, but the interpretation of mtDNA evidence is con-troversial. More than 2,600 sequences of the first hy-pervariable mitochondrial control region were analyzed for geographic patterns in samples from Europe, the Near East, and the Caucasus. Two autocorrelation sta-tistics were used, one based on allele-frequency differ-ences between samples and the other based on both se-quence and frequency differences between alleles. In the global analysis, limited geographic patterning was ob-served, which could largely be attributed to a marked difference between the Saami and all other populations. The distribution of the zones of highest mitochondrial variation (genetic boundaries) confirmed that the Saami are sharply differentiated from an otherwise rather ho-mogeneous set of European samples. However, an area of significant clinal variation was identified around the Mediterranean Sea (and not in the north), even though the differences between northern and southern popula-tions were insignificant. Both a Paleolithic expansion and the Neolithic demic diffusion of farmers could have determined a longitudinal cline of mtDNA diversity. However, additional phenomena must be considered in both models, to account both for the north-south dif-ferences and for the greater geographic scope of clinal patterns at nuclear loci. Conversely, two predicted con-sequences of models of Mesolithic reexpansion from gla-cial refugia were not observed in the present study