Reconstructing diet after the fall of the Wari Empire in the central Andean Highlands: A study of human dental calculus

Stable isotopes from bones and teeth have been used to reconstruct human lifeways in bioarchaeological research for over 30 years. Recently, there have been efforts to use less invasive methods of analysis that meet ethical standards and do not compromise the integrity of human skeletal remains. To that end, this study examines dental calculus from human teeth as a proxy for paleodietary reconstruction. This current work builds on a handful of studies that have tested the use of dental calculus for reconstructing diet, which have shown mixed results. This study contributes to those ongoing efforts to improve methods and capacities in paleodiet research. The sample is comprised of dental calculus from individuals from the Wari (600–1000 CE) and post-Wari periods (1000–1400 CE). Individuals from both time periods with stable carbon and nitrogen isotope data from the calculus are directly compared to the stable isotope results from human bone collagen, dental carbonates, and bone carbonates. Results from dental calculus show δ¹³C that range from -20.5 ‰ to −12.3 ‰, consistent with the use of C₄ plants (maize) as a major component of the diet. The δ¹³C from calculus are isotopically lighter and more varied than those obtained from collagen, and this is likely explained by the distinct composition of calculus compared to that of bone collagen and apatite. The δ¹⁵N from calculus range from +8.9 ‰ to +18.8 ‰, which is heavier than expected for highland maize-based diets in the Peruvian Andes. This may be explained by ¹⁵N enrichment from aridity or crop fertilization (e.g., camelid dung), especially during the post Wari period, a time of social upheaval and severe drought. The differences in stable isotope values may also be partially explained by the diet-sourced isotopes in bone collagen (e.g., averaging the last 5–10 years of life) versus that of dental calculus (e.g., averaging the last few years of life). Documenting these differences in stable isotope ratios from distinct components may aid in richer understandings of past diets and provide additional ways to compare diet through time and space. Indeed, as more researchers begin analyzing the stable isotope ratios from dental calculus, we can minimize destructive techniques and make direct comparisons between studies that use dental calculus. We suggest that this is an important expansion of our analytical toolkit.