Microevolution of human archaic groups of Arica, northern Chile, and its genetic contribution to populations from the Formative period

The microevolution of the archaic populations from Chile's northern coast and its morphological contribution to Formative period groups was studied. The sample comprised 181 individuals belonging to two Archaic (Morro-Uhle and Morro 1-1/6) and one Formative (Playa Miller-7 [Plm-7]) series of the coast and one sample from the Formative (Alto Ramírez) exhumed at the Azapa Valley. A total of 29 metric variables of the cranium were analyzed. Biological variability was assessed using discriminant analysis and Mahalanobis' D2 distance stadistic (MDS). Population structure was inferred using a method based on quantitative genetic theory that predicts a lineal relationship between average within-group phenotypic variance and group distance to the population centroid. The four samples studied proved to be different from a morphologic point of view. The greatest distance was observed between Plm-7 (coast Formative) and Alto Ramirez (valley Formative), the least between Morro-Uhle and Morro 1-1/6, the remaining distances presenting intermediate values. Regarding the total population, the most divergent group was Alto Ramírez and the least divergent was Morro1-1/6. A gradual biologic change was observed between Archaic (Morro Uhle and Morro 1-1/6) and coastal Formative populations (Plm-7) pointing to a morphological (genetic) contribution of Archaic fishermen to Formative population of Chile's northern coast, without excluding gene flow from other groups of the South Central Andean Area.