Kinship in both sexes, in individuals with and without cranial modification, and its relationship with cultural practices in the ancient population of San Pedro de Atacama

The study of kinship is fundamental to understanding past societies because it provides information about the social organization of populations. This paper evaluates the phenotypic variation in both sexes and in groups with and without artificial modification of the skull in the ancient population of the oasis of San Pedro de Atacama (SPA), northern Chile. This information is used to infer kinship, the number of migrants per generation and the possible relationship with sociocultural factors. To achieve the objective, craniometric characters and a sample of 592 individuals from different sites and cultural periods of the SPA population are used. Phenotypic variation within and between groups is assessed by multivariate statistical analysis and kinship is estimated by applying methods derived from quantitative genetics. Postmarital residence is obtained by comparing the variances of both sexes between sites, periods and groups with and without skull modification. In general, the results show greater male than female mobility, or similar mobility in both sexes, indicating a matrilocal or bilocal postmarital residence pattern. In particular, greater female than male mobility is observed between ayllu (social organization formed by individuals related by kinship and economic ties) in individuals with artificial modification of the skull, supporting a patrilocal postmarital model. Additionally, it was observed that individuals with head modification have lower level of kinship among themselves and greater mobility than the group that did not modify their head, establishing that this cultural behavior plays a relevant role in the genetic structure of the population.