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.

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.

One of the most interesting issues of the interface between biology and culture is the artificial deformation of the skull. This modification is produced during early morphogenesis through the use of devices that alter the normal growth and development, to obtain a culturally established model. This paper, using a large cranial sample from the South Central Andes (1586 individuals), describes and documents a detailed morphometric study of the changes affecting the vault, cranial base, face, orbits and nasal region resulting from the tabular erect (TE), tabular oblique (TO), circular erect (CE) and circular oblique (CO) deformations with respect to the model without deformation. Data from 17 metric variables were processed by a one-way ANOVA and LSD test for paired comparisons. All of the deformation types produce significant morphometric divergence in most of the anatomical structures of the skull. The TE exhibits: a restriction of antero-posterior growth producing expansion in cranial width and height, frontal flattening, shortening of the face and cranial base, widening of the face, increased nasal and orbit height (ORH) and a foramen magnum size increase. The TO exhibits: most change reflected in the widening of the cranial vault, shortening of the cranial base and face, frontal flattening, increased nasal and ORH and foramen magnum size decrease. The CE style exhibits: a decrease in cranial width and strong increase in the cranial height, a reduction in frontal width, expansion of the cranial base and face, increased nasal and ORH, orbital widening and a foramen magnum size increase. The CO style exhibits: a decrease of the cranial vault's width and height, expansion along its length, stretching of the cranial base and face, reduced frontal width, fronto-malar and biorbitary elongation of the face and further development of foramen magnum.

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