Stable isotope evidence for the participation of commoners in Inka khipu production.

This study presents previously unknown evidence about the social status of Inka-era khipu experts. A lack of physical evidence hinders our understanding of the specialists who made Inka khipus (knotted cords that served as writing). On the basis of primarily Spanish-language colonial chronicles, it is thought that khipus were created exclusively by male bureaucratic elites. We analyzed Inka khipu, KH0631, whose primary cord is composed of human hair. Historically, human hair on a khipu served as a "signature" to indicate the khipu's creator. Recent advances in elemental analysis-isotope ratio mass spectrometry allowed us to undertake simultaneous carbon, nitrogen, and sulfur measurements from a single KH0631 hair sample, revealing that this individual consumed a diet characteristic of low-ranking commoners. This finding suggests that commoners participated in Inka khipu production.