Previous archaeological studies suggest that terminal Middle Horizon Tumilaca populations (cal A.D. 950–1150) of the middle Moquegua Valley represent direct descendants of earlier Chen Chen-style Tiwankau colonists of the region. This study tests this idea by comparing dentally derived biodistance analyses of Tumilaca, Chen Chen-style, Tiwanaku, and other regional samples. The results indicate that the Tumilaca and Chen Chen-style mortuary samples are similar to one another suggesting that these populations might share an ancestral-descendant relationship. The phenetic relations of the Tumilaca and Chen Chen to other regional samples are also discussed.

This investigation uses a bioarchaeological approach to test the existence of pre-Inka colonists within the Andean coastal valleys of Moquegua, Peru, and Azapa, Chile, as predicted by Murra's (1972) classic model of verticality. The archaeological evidence and biodistance results obtained using genetically controlled dental traits from 859 skeletal and mummified remains indicate that the Late Intermediate period (A.D. 1100-1476) coastal Chiribaya people of the Moquegua Valley, Peru, likely represent descendants of altiplano populations that migrated to the coastal region following the disintegration of the Middle Horizon (A.D. 750-1100) Tiwanaku colony located in the middle Moquegua Valley. In the neighboring Azapa Valley, Chile, genetic change among prehistoric populations was due to gradual in situ microevolution of local populations rather than colonization by altiplano people. Coastal populations of the Azapa Valley maintained biocultural continuity with the Archaic period Chinchorro coastal population. It is concluded that Murra's model of direct verticality should be evaluated using both biological and archaeological data on a case-by-case basis.