Recordkeeping wasn’t a mundane statistical task in the Incan empire—it was an artform. Instead of solely relying on scribes to maintain ledgers on subjects like trade, agricultural yields, and labor, the ancient South American culture also turned to a documentation tool called the khipu. Each khipu works like its own spreadsheet, with several knotted cords representing decimal numbers that are all hung from an anchor cord woven from human hair.
Archaeologists have long suspected khipus were highly personal tools, with the hair serving as the author’s “signature.” Spanish colonial accounts even speak of the Incan elite burying specialized, khipu-wielding male bureaucrats known as khipukamayuqs with their knotted assemblies upon their deaths. But according to new analysis recently detailed in the journal Science Advances, the khipu may have been a more common sight throughout the extremely class-based empire.
The key evidence comes from diet. A team of international researchers used radiocarbon dating combined with isotope ratio mass spectrometry to assess a sample khipu’s age, as well as its human hair’s carbon, nitrogen, and sulfur levels. The khipu-in-question dates to around 1500 CE, and originates from an Incan whose diet mainly consisted of greens and tubers. Since wealthier and respected Incan elites ate much meat and maize, the khipu specimen likely belonged to a commoner.
Additional isotopic analysis further supports this theory. The hair’s oxygen and hydrogen levels show that the mystery individual lived at an altitude roughly 8,560 to 9,186 feet above sea level.
“In other words, the individual lived in the highlands, relatively far from the Pacific Ocean,” the study’s authors explained. “This finding correlates with the low level of marine resources in the diet. Our results also suggest that the individual lived in southern Peru or northern Chile.”
It’s impossible to reach any definitive answers from a single khipu, which is why the team hopes to conduct similar isotopic analysis on other examples in the future. At the very least, however, the researchers believe their work “suggests that commoners participated in Inca khipu production.”
Incidentally, the study also highlights the importance and value of Indigenous primary sources. Accounts of expanded khipu use date as far back as the 16th century, when Quechua noble and cultural chronicler Felipe Guaman Poma de Ayala wrote that Incan women “[kept] track of everything” on their khipus.
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