Isotopic study of maize exploitation during the Formative Period at Pacopampa, Peru

Maize (Zea mays) was an important staple and ceremonial food in the pre-Columbian Andean world. Previous researchers have studied maize agriculture in early ancient Andean society by examining macroand microbotanical remains. However, isotope analyses of human remains have shown that maize was not a primary food resource during the Formative Period (1800–1 cal BC). Although a few studies have suggested that maize was consumed in this period, we know little about how the dietary role of maize differed across the Andean society and how it changed over time. This study measures carbon and nitrogen isotope ratios from human and animal bone collagen samples and human tooth enamel samples excavated from the Pacopampa archaeological site in the highlands of northern Peru in order to better understand maize consumption in this period. The site dates to the Middle to Late Formative Periods (1200–700 cal BC, 700–400 cal BC) and the Early Cajamarca phase (cal AD 200–450). The findings indicate an increase in C4 resource consumption during the Late Formative Period—an increase that we attribute directly to maize and indirectly to domesticated animals. Although dietary variation related to social stratification was insignificant at this site, it has been reported at and between some coeval sites. Thus, we conclude that when these populations began exploiting C4 resources, their strategic use of these resources varied depending on the site. This study suggests that the use of maize during the Formative Period was probably greater and earlier than reported in previous isotope studies. In addition, maize utilization for domestic animals in this period, which has rarely been mentioned, was also important.