Cautionary tales on the identification of caffeinated beverages in North America

In recent years several studies have attempted to understand the use of caffeinated beverages in North America before the coming of Europeans using absorbed residues. These studies have focused on the two key plant sources of caffeine in North America: Theobroma cacao (cacao) and Ilex vomitoria (yaupon holly). The authors initiated a study to explore the possibility that one or both plants were used at the Mississippian period (900-1600 CE) center of Etowah in northern Georgia. In the process, a series of problems with methodologies in use were revealed. Key among those were limitations on the methods used to identify ancient caffeinated beverage residues, distinguish them from modern contamination, and differentiate residues made by each plant. In this paper we explore what our data from the Etowah site reveal about methodologies currently in use and make suggestions for future studies of residues created by caffeinated beverages in North America.