Multivarate techniques can be used to condense the information for a large number of loci and alleles into one or a few synthetic variables. The geographic distribution of synthetic variables can be plotted by the same technique used in mapping the gene frequency of a single allele. Synthetic maps were constructed for Europe and the Near East, with the use of principal components to condense the information of 38 independent alleles from ten loci. The first principal component summarizes close to 30% of the total information and shows gradients. Maps thus constructed show clines in remarkable agreement with those expected on the basis of the spread of early farming in Europe, thus supporting the hypothesis that this spread was a demic spread rather than a cultural diffusion of farming technology.

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The genetic information for this work came from a very large collection of gene frequencies for "classical" (non-DNA) polymorphisms of the world aborigines. The data were grouped in 42 populations studied for 120 alleles. The reconstruction of human evolutionary history thus generated was checked with statistical techniques such as "bootstrapping." It changes some earlier conclusions and is in agreement with more recent ones, including published and unpublished DNA-marker results. The first split in the phylogenetic tree separates Africans from non-Africans, and the second separates two major clusters, one corresponding to Caucasoids, East Asians,'Arctic populations, and American natives, and the other to Southeast Asians (mainland and insular), Pacific islanders, and New Guineans and Australians. Average genetic distances between the most important clusters are proportional to archaeological separation times. Linguistic families correspond to groups of populations with very few, easily understood overlaps, and their origin can be given a time frame. Linguistic superfamilies show remarkable correspondence with the two major clusters, indicating considerable parallelism between genetic and linguistic evolution. The latest step in language development may have been an important factor determining' the rapid expansion that followed the appearance of modern humans and the demise of Neanderthals.The reconstruction of human phylogeny from contemporary genetic information was first attempted (1-4) by the use of gene frequencies of 20 alleles from five major blood-group systems known from 15 populations. The genetic information from all genes was cumulated by calculating a "genetic distance" between pairs of populations. Two independent methods developed for the purpose were used to reconstruct the phylogeny, with very similar results. One of them was based on independence of evolution in the branches resulting after every fission, and the other on maximum parsimony; neither, however, can define an origin (a "root") for the tree. When only information internal to the data set is used, it is necessary to assume constant evolutionary rates for setting a root. When this hypothesis was superimposed on constructed trees, the root separated African plus European populations on one side and the rest of the world on the other. The later addition of more genes (5), including HLA (6), caused little change in the shape of the phylogenetic tree.Many protein and enzyme polymorphisms were detected in the 1960s and 1970s by electrophoretic methods but were initially tested on few samples. By using only three populations (Africans, Europeans, and East Asians), Nei (7) was able to consider many more genes. He concluded that blood groups and enzyme polymorphisms gave different results with respect to the location of the root, with blood groups still showing greater similarity between Africans and Europeans than between Europeans and East Asians, thus confirming earlier results on the position of the root. With enzymes and protein...

Geographic expansions are caused by successful innovations, biological or cultural, that favor local growth and movement. They have had a powerful effect in determining the present patterns of human genetic geography. Modern human populations expanded rapidly across the Earth in the last 100,000 years. At the end of the Paleolithic (10,000 years ago) only a few islands and other areas were unoccupied. The number of inhabitants was then about one thousand times smaller than it is now. Population densities were low throughout the Paleolithic, and random genetic drift was therefore especially effective. Major genetic differences between living human groups must have evolved at that time. Population growths that began afterward, especially with the spread of agriculture, progressively reduced the drift in population and the resulting genetic differentiation. Genetic traces of the expansions that these growths determined are still recognizable.

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Principal component maps of the gene arrangement frequencies of 108 natural populations in Europe, North Africa and the Middle East were prepared to investigate the evolutionary forces shaping the geographic variation of inversion frequencies. Principal component maps were also prepared from ten climate variables at 347 localities of the same region. The first inversion principal component (18% of total variation) showed a N-S cline strikingly similar to the pattern exhibited by the first principal component of climatic variables. This resemblance is interpreted as showing the outcome of a selective process, which favors the increase in frequency of the Standard gene arrangements when moving to the north. This interpretation is corroborated by the fact that such clines were formed in South and North America, following recent colonization by this species. Patterns shown by the second (12% of total variance) and third (8% of total variance) principal components are interpreted as related to historical events, the migrational advance to the north after the end of the last glaciation and the locations of the species refugia at that time.

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We report an autocorrelation study of 11 enzyme loci detected by starch gel electrophoresis in 14 populations over the Italian biogeographical range of beech (Fagus sylvatica L.). In line with previous studies of beech and other forest tree species a low level of spatial autocorrelation was detected. No correlation between the amount of microspatial structuring of genetic variability in different populations and environmental (latitude, longitude, altitude), structural (mean and standard deviation of tree size) and genetic characteristics (mean expected heterozygosity, mean F1) was found. No significant differences in the amount of spatial structuring seem to exist among loci if low heterozygosity loci are excluded from the analysis.