Landscape bioarchaeology at Pacatnamu, Peru: inferring mobility from δ13C and δ15N values of hair

Stable carbon- and nitrogen-isotope ratios were measured for segments along the shafts of hair from eight individuals from the site of Pacatnamu, located in the Jequetepeque Valley on the north coast of Peru. All are from known grave contexts dating from Moche (ca. 450–750 A.D.) to Lambayeque periods (ca. 900–1100 A.D.). The mean δ13C and δ15N values of hair segments from individuals are comparable to those of bone, and demonstrate increased consumption of marine resources in the Lambayeque times relative to the Moche period.Sequential analyses of the hair, however, reveal that intra-individual dietary variation occurring over periods of months is even greater than that between cultural periods. The frequency, timing and amplitude of these shifts are not what would be expected of seasonal differences. Instead, they more likely indicate geographic relocations resulting from short-term travel between regions with different food resources, for example, the coast and the highlands. Adult males exhibit more dramatic shifts than the children and there is no evident patterning in the residence place of individuals close to the time of death. There are several possible reasons for this variability. First, as previously proposed, Pacatnamu may have been a pilgrimage site. Second, there may have been coastal-highland movement, indicating complex utilization of the landscape, possibly including the verticality thought to characterize many ancient Peruvian exchange systems. Finally, Pacatnamu may have functioned as an administrative center for a large geographic area. Thus, the reason for these geographic relocations may have been religious, economic or administrative in nature.