Guinea pigs, or cuy, are a delicacy in the Andes, as shown in Marcos Zapata's 1755 painting, The Last Supper. However, they can also be used to determine the isotopic signatures of geologic regions in the Andes. By comparing the cuy data with the isotope ratios found in archaeological human remains, bioarchaeologists can determine where an individual lived during the first and last years of life. Kelly J. Knudson and her colleagues have used strontium isotope analysis at Tiwanaku- and Chiribaya-affiliated sites to elucidate the nature of Tiwanaku influence from AD 500 to 1100.

In addition , Kelly J. Knudson and Christina Torres-Rouff of The Colorado College are currently combining biogeochemistry and bioarchaeology to examine biological and cultural identity during and after periods of Tiwanaku influence. With funding from the National Science Foundation, they are currently investigating identity construction, projection, and manipulation in northern Chile from AD 750 to 1470. Archaeological human remains from sites in the San Pedro de Atacama oasis and as well as the Loa River Valley site of Caspana, shown in the accompanying photo, will be included in this project.

On the South Coast of Peru, Kelly J. Knudson, Sloan Williams, Ryan Williams, Kathleen Forgey and Rebecca Osborn have completed a study of the geographic origins of Nasca trophy heads from the Field Museum of Natural History. Using strontium, oxygen and carbon isotopes, they determined that the trophy heads, as shown here on a Nasca ceramic vessel (plate 23, Kroeber and Collier 1998), likely derived from the Nazca Drainage. For more information on this work, see Discovery News, History Today, the Medill Reports, Science News, and Wired Science.