Clinal patterns of autosomal genetic diversity within Europe have been interpreted in previous studies in terms of a Neolithic demic diffusion model for the spread of agriculture; in contrast, studies using mtDNA have traced many founding lineages to the Paleolithic and have not shown strongly clinal variation. We have used 11 human Y-chromosomal biallelic polymorphisms, defining 10 haplogroups, to analyze a sample of 3,616 Y chromosomes belonging to 47 European and circum-European populations. Patterns of geographic differentiation are highly nonrandom, and, when they are assessed using spatial autocorrelation analysis, they show significant clines for five of six haplogroups analyzed. Clines for two haplogroups, representing 45% of the chromosomes, are continentwide and consistent with the demic diffusion hypothesis. Clines for three other haplogroups each have different foci and are more regionally restricted and are likely to reflect distinct population movements, including one from north of the Black Sea. Principal-components analysis suggests that populations are related primarily on the basis of geography, rather than on the basis of linguistic affinity. This is confirmed in Mantel tests, which show a strong and highly significant partial correlation between genetics and geography but a low, nonsignificant partial correlation between genetics and language. Genetic-barrier analysis also indicates the primacy of geography in the shaping of patterns of variation. These patterns retain a strong signal of expansion from the Near East but also suggest that the demographic history of Europe has been complex and influenced by other major population movements, as well as by linguistic and geographic heterogeneities and the effects of drift.

Our closest living relatives, chimpanzees and bonobos, have a complex demographic history. We have analyzed the high-coverage whole genomes of 75 wild-born chimpanzees and bonobos from ten countries in Africa. We find that chimpanzee population sub-structure makes genetic information a good predictor of geographic origin at country and regional scales. Most strikingly, multiple lines of evidence suggest that gene flow occurred from bonobos into the ancestors of central and eastern chimpanzees between 200 and 550 thousand years ago (Kya), probably with subsequent spread into Nigeria-Cameroon chimpanzees. Together with another possibly more recent contact (after 200 Kya), bonobos contributed less than 1% to the central chimpanzee genomes. Admixture thus appears to have been widespread during hominid evolution.

Congenital deafness accounts for about 1 in 1000 infants and approximately 80% of cases are inherited as an autosomal recessive trait. Recently, it has been demonstrated that connexin 26 (GJB2) gene is a major gene for congenital sensorineural deafness. A single mutation (named 35delG) was found in most recessive families and sporadic cases of congenital deafness, among Caucasoids, with relative frequencies ranging from 28% to 63%. We present here the analysis of the 35delG mutation in 3270 random controls from 17 European countries. We have detected a carrier frequency for 35delG of 1 in 35 in southern Europe and 1 in 79 in central and northern Europe. In addition, 35delG was detected in five out of 376 Jewish subjects of different origin, but was absent in other non-European populations. The study suggests either a single origin for 35delG somewhere in Europe or in the Middle East, and the possible presence of a carrier advantage together with a founder effect. The 35delG carrier frequency of 1 in 51 in the overall European population clearly indicates that this genetic alteration is a major mutation for autosomal recessive deafness in Caucasoids. This finding should facilitate diagnosis of congenital deafness and allow early treatment of the affected subjects.

It is often taken for granted that the human species is divided in rather homogeneous groups or races, among which biological differences are large. Studies of allele frequencies do not support this view, but they have not been sufficient to rule it out either. We analyzed human molecular diversity at 109 DNA markers, namely 30 microsatellite loci and 79 polymorphic restriction sites (restriction fragment length polymorphism loci) in 16 populations of the world. By partitioning genetic variances at three hierarchical levels of population subdivision, we found that differences between members of the same population account for 84.4% of the total, which is in excellent agreement with estimates based on allele frequencies of classic, protein polymorphisms. Genetic variation remains high even within small population groups. On the average, microsatellite and restriction fragment length polymorphism loci yield identical estimates. Differences among continents represent roughly 1͞10 of human molecular diversity, which does not suggest that the racial subdivision of our species ref lects any major discontinuity in our genome.In 1972, Richard Lewontin analyzed allele frequencies at 15 protein loci and concluded that 85% of the overall human genetic diversity is represented by individual diversity within populations (1). Differences among seven racial groups accounted for less than 7% of the total. Nei and Roychoudhury reached a similar apportionment of genetic diversity among populations from three continents (2). Although these results were repeatedly confirmed by studies of protein markers (3-5), the idea that the human species is deeply subdivided into races has not disappeared (6, 7). Reasons for this include some perceived discontinuity among populations, usually reported for quantitative traits (6), and the possibility that protein markers, including blood groups, may not exhaustively describe genetic variation, leaving open the possibility that the undetected variation might show a different pattern.In this study, we analyzed how DNA variation is distributed at 109 loci (Fig. 1). Based on the lengths and frequencies of the microsatellite alleles and on the frequencies of allelic variants at restriction fragment length polymorphism (RFLP) loci, we quantified the differences among members of the same population, among populations of the same continent, and among four or five geographical groups. Materials and MethodsThree largely independent sets of genetic data were used in this study. The microsatellite database comprises individual allele lengths for 29 repeats and one tetranucleotide repeat of chromosomes 13 and 15. This is the set of data used by Bowcock et al. (8) from which we excluded nonhuman primates. The map distances between adjacent loci, except eight of them, are such that linkage disequilibrium can hardly be considered a major disturbing factor. Fourteen populations are included, for an overall sample size of 148. However, for no marker was a complete set of 296 chromosomes available. The mi...