The representativeness of the dental calculus dietary record: insights from Ta\xef chimpanzee faecal phytoliths

Robert C Power,Roman M Wittig,Kornelius Kupczik,Jeffery R Stone,Ellen Schulz-Kornas

doi:10.1007/s12520-021-01342-z

Abstract

In recent years, new applications of microremain dietary analysis using dental calculus as a source of dietary data on ancient human subsistence and behaviours have accelerated. The dental calculus of contemporary human and non-human populations with known diets have been used as reference datasets, including the chimpanzees of Taï National Park (Côte d'Ivoire), but explaining the preservation mechanism involved is challenged by our incomplete knowledge of the microremain content within the diets of these reference populations and our rudimentary information on microremain incorporation into dental calculus. Here, we analyse phytoliths in faecal samples to assess to what extent plant phytoliths of a diet are reflected in the dental calculus as well as in the egested faeces. In this study, we identify and document the faecal phytolith assemblages as an indicator of plant consumption in two Western chimpanzees of the Taï National Park (Côte d'Ivoire) before (wet season), during (dry season) and after (dry season) a dust-rich period. Moreover, observational dietary records of these two individuals were compiled to improve the interpretability of this dental calculus phytolith dataset. The faecal phytolith assemblages vary significantly across samples in terms of abundance and diversity. The most common phytolith morphotypes were eudicot plates, single-cell and multi-cell tracheids, monocot rugulose and echinate spheroids and, to a lesser extent, unspecified thick and thin elongates. High loads of grit and other micro-remains (e.g. diatoms) are found during the dry period. Using observational dietary records as a starting point and our faecal results as a terminus, we consider how dental calculus can accumulate phytoliths. Our findings enable identification of the phytolith morphotypes that are under-represented in dental calculus, which is highly informative for future dental calculus research strategies.

Highlights

In recent years, human dental calculus has received increased interest as a source of life history information
We examined phytolith assemblages from faeces of Western chimpanzees of the Taï National Park (Côte d'Ivoire) (Schulz-Kornas et al 2019) to document the phytolith types that are missing from the published chimpanzee dental calculus (Power et al 2015) and possibly systematically underrepresented across dietary studies
The phytolith morphotypes of the faecal samples of the Taï chimpanzees are largely comparable to published Kibale chimpanzee faecal phytolith datasets

Summary

Introduction

Human dental calculus has received increased interest as a source of life history information. Researchers have examined dental calculus from populations with well-documented diets, including living human forager-horticulturists from Namibia and skeletal wild chimpanzees from Côte d’Ivoire, with local reference plant collections to measure the ability of calculus to reflect diet in these two environments (Leonard et al 2015; Power et al 2015). These studies have set a benchmark on dental calculus’ dietary micro-remains coverage, but they highlight discrepancies that exist between diet and dental calculus microremain assemblages. Specific micro-remains from staple and non-staple foods have been found to be overrepresented, such as the starch grains of maize (a Twe staple) and the phytoliths of oil palm (a minor chimpanzee food) (Leonard et al 2015; Power et al 2015)

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