To obtain a better understanding of the social interactions that occurred between the Tiwanaku state of highland Bolivia and the Atacama area of north Chile and to explore the relationship between cranial deformation and group identity in the Atacama, I examined skeletal materials from two sites, Toconao Oriente (100 BC to AD 300) and Solcor 3 (AD 400 to 900). Cranial vault modification serves to delimit social boundaries both within and between groups. Owing to its permanence and to the fact that it must be performed by adults on young children, it serves as a powerful, constant, and visually salient symbol of social identity. My working hypothesis was that the increase in social complexity associated with increased Tiwanaku influence on the Atacameño culture should be reflected in the use of more complex symbolic systems for maintaining social boundaries, including an increase in the elaborateness of the practice of cranial vault modification.

These collections were studied to obtain evidence of change in the pattern of vault modification and correlations between presence and type of foreign goods, mortuary goods and tomb structure, and types of cranial vault modification found in specific burials in order to explore this hypothesis. The results show that the frequency of skulls with some form of cranial vault modification at Toconao Oriente and Solcor 3 is similar and the sites do not differ significantly in this respect. No pattern is evident in the relationship between the presence of cranial deformation and Tiwanaku artifacts in the population from Solcor 3. The increase in proportion of individuals with annular deformation from Toconao Oriente to Solcor 3 could reflect a cultural influence from Tiwanaku. Individuals at Solcor 3 may have been using cranial vault modification as a signifier of membership or alliance with this prestigious foreign group. These cranial modification data do not support the hypothesis that emissaries of the Tiwanaku state were buried at Solcor 3. However, by adopting a non-local style of cranial shape, the Solcor 3 population may have been strengthening and making overt its ties to this outside group.