Search

The genetic structure, kinship and type of post-marital residence are studied in four native groups of the Gran Chaco, through the analysis of somatometric traits. The sample used was published by Lehmann-Nitsche (1907) and is represented by 158 individuals of both sexes. To meet the objectives, methods and techniques of multivariate statistics and population genetics of quantitative traits were applied. The results show a genetic divergence (F ST ) of 0.047, a greater kinship between chorote and mataco, a significant isolation of the chiriguano, an important interaction of the chorote with the rest of the groups, a greater regional mobility of males than of the women, and a matrilocal or bilocal post-marital residence system.

In this article we study the phenotypic structure, biological relationships and evolutionary factors that acted on the biological diversity observed in the prehistoric groups that inhabited Northwest Argentina (NWA). The collections used belong to different subareas and periods of the development of this region. In this study 15 metric traits of the skull were used. To achieve the proposed objective, models derived from population genetics, multivariate statistical analysis, geo-referenced map and phenotypic correlation between geographical and biological distances were applied. The total genetic divergence (F ST ) is 16% and within subregions it varies between 2% and 10%. The correlation (r) between geographic and phenotypic distances among all samples in NWA is 0.3 and within subregions it varies between -0.16 (Quebrada de Humahuaca) and 0.7 (Puna de Jujuy). The analysis of georeferenced data indicates two phenotypic gradients in NWA. The results show a varied evolutionary scenario, characterized by an important population structure produced by a set of evolutionary factors (genetic isolation, non-random mating, effective size and different rates of genetic interaction between subpopulations).

The existing biocultural links are analyzed among ancient inhabitants of the Cochabamba valleys (Bolivia) from the Formative and Tiwanaku periods, coastal and inland Azapa region (Chile) from the Late Archaic to the Late periods, and the Atacama Desert oases (Chile) from the Formative period to the time of European contact. Craniometric information obtained from a sample of 565 individuals from different sites of the studied regions was evaluated using methods derived from quantitative genetics and multivariate statistical analysis techniques. It is shown that during the Formative and Tiwanaku periods inhabitants of the Cochabamba valleys maintained contact with the population of northern Chile. This contact was more fluid with the people from the interior valley of Azapa than it was with the settlers of San Pedro Atacama (SPA). An important biological affinity in the Late Period between the inhabitants of the Azapa valley and the late SPA groups is also examined. The Late-Inca Catarpe SPA sample shows a broad genetic variability shared with the majority of the groups studied. The results reaffirm the differences between the coastal and interior Azapa valley groups and strengthen the hypothesis of two pathways to populating the south central Andean area. The divergence observed among subpopulations can be explained by the spatiotemporal dispersion between them, genetic drift dispersion compensated by the action of gene flow, and cultural norms that regulate within group mating., (© 2014 Wiley Periodicals, Inc.)

The peopling of the south-central Andean region can be determined by exploring a combination of cultural, economic, and biological factors that influence the structure of populations and determine particular dispersals of gene frequencies. Quantitative characters from 1,586 adult crania of both sexes from northern Chile, northwestern Argentina, and the Cochabamba valleys in Bolivia were analyzed employing multivariate statistical analyses. Biological distances, representing phenotypic variation between these regions and their subregions, were studied within a population genetics framework. An analysis of Mahalanobis D(2) distances establishes two principle directions of interaction: the first between the Cochabamba valleys and northern Chile, and the second between the Cochabamba region and northwestern Argentina. The Chile and Argentina regions are shown to be less related to each other than each is to the Bolivian region. A higher mean genetic divergence is found for the entire region (F(ST) = 0.195); with northwestern Argentina having the highest spatial isolation (F(ST) = 0.143) and northern Chile the lowest (F(ST) = 0.061). These results allow us to propose a populating model based on the dispersion of several lines from a common ancestral population similar to those who inhabited the Cochabamba valleys. These lines differentiated themselves in time and space according to the effective size and the rate of gene flow, eventually producing the human groups which inhabited the valleys of northern Chile and northwestern Argentina.

The phenotypic variance (V(P)) may be divided into the genetic variance (V(G)), the general environmental variance (V(Eg)), and the special environmental variance (V(Es)). The latter is estimated through repeatability calculation (b). This value is considered the upper limit of heritability and represents maximum genetic variance proportion (V(Gm) = V(G) + V(Eg)) in relation to V(P) (b = (V(G) + V(Eg))/V(P)). This process allows an improved determination of biological relationships among groups from estimators maximizing the genetic information of quantitative characters. Two hundred and thirty-seven individuals inhabiting the northern coast of Chile for 4,000 years were taken as a sample. Measurement was made of six metric characters at both sides of the cranium. Special environmental values (es) were obtained by regression. The difference between these values and the phenotypic values (p) consists in the genetic values plus the general environmental values (g + eg). A mean b value of 0.83 indicated that V(Es) represents 17% of V(P). The results showed: 1) high stability of the maximum genetic variance in time and space, 2) high correlation between the biological relationships model, the phenotypic model, and the maximum genetic model, and 3) random distribution of the nongenetic variation, as expected from the quantitative genetics theory. These results support the use of phenotypic data for the interpretation of the evolution history of prehistoric populations., ((c) 2006 Wiley-Liss, Inc)

The present paper studies the evolutionary process operating on prehistoric groups from the Azapa valley and coast (northern Chile). The sample consists of 237 crania from the Archaic Late, Early Intermediate, Middle, Late Intermediate, and Late periods. Six metric variables were used, which were transformed to eliminate the special environmental component and to increase the proportion of genetic variance. Population structure was assessed using a method based on quantitative genetic theory, which predicts a lineal relationship between average within-group phenotypic variance and group distance to the population centroid. Results indicate that 17.5% of the total variance accounts for special environmental variance. An excess in extraregional genetic flow is observed in the population corresponding to the Early Intermediate period in the valley. A reduced differentiation is observed between Archaic and Early Intermediate coastal groups, as well as between the latter and the inhabitants of the valley in the same period. Genetic differences between both areas increased substantially since the Middle period. Evidence indicates that long-range gene flow was lower on the coast than in the valley, the lowest estimated Fst being 0.0199 for the total population (coast and valley), 0.0111 for the coastal population, and 0.0057 for the valley. Results are discussed in terms of regional archeological and ethnohistorical evidence, and a microevolutionary model is presented to account for the biological history of the population., (Copyright 2002 Wiley-Liss, Inc.)