The representativeness of the dental calculus dietary record: insights from Taï chimpanzee faecal phytoliths

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.

Beyond dirty teeth: Integrating dental calculus studies with osteoarchaeological parameters

“…Ethnographic research on modern populations has shown staple starchy food, such as maize, eaten once a day was only found in 30% of the calculus samples of the individuals who took part in the study ( Leonard et al, 2015 ). More recently, research by Power et al (2021) has shown that phytoliths too are underrepresented in dental calculus material. These studies show that starch and phytoliths, the two key typologies of plant remains found in dental calculus, do not reflect the variety of plant food ingested.…”

“…Further experimental work and research is needed to clarify what portion of the diet is visible in dental calculus and how methodologies of extraction of remains can be improved. All above issues have been discussed in recent reviews and methodological work in the field and we refer to them for further in depth reading (see Hardy et al, 2018 ; Power et al, 2021 ; Radini et al, 2017 ). Nevertheless, despite the above limitations, there is widespread agreement in the dental calculus research community that this deposit offers great potential to provide new insights about ingested items in ancient individuals, especially plant remains ( Hardy et al, 2018 ).…”

Investigating Biases Associated With Dietary Starch Incorporation and Retention With an Oral Biofilm Model

“…The authors found significantly more starches with the EDTA extraction method than the HCl extraction method; however, as noted by the authors, comparisons involving archaeological calculus are problematic due to variability between and within individuals. Studies conducted on modern humans (Leonard et al, 2015) and non-human primates (Power et al, 2015;Power et al, 2021) have explored how well microremains (phytoliths and starches) extracted from dental calculus represent the actual dietary intake. These studies are justifiably limited, despite meticulous documentation and observation, due to unknown variables and uncertainty involved in this kind of in vivo research.…”

Interpreting phytoliths assemblages at chimpanzee (Pan troglodytes verus) nut-cracking sites in Bossou Forest, Guinea

“…Diet composition estimates using phytolith reference libraries from plants eaten by extant primates been recently explored. Phytolith assemblages have been correlated with primate enamel thickness (Power et al 2015), and interpretations of phytolith assemblages in faeces of east and west African chimpanzees (Phillips & Lancelotti 2014; Power et al 2021) have revealed components of diet that are less detectable at the macroscopic level. Relevant for this study and for future work is Power et al’s (2021) findings for the nut-cracking chimpanzees of Taï Forest; oil palm phytoliths were “overrepresented” in dietary composition estimates based on analyses of their faeces and dental calculus.…”

“…Relevant for this study and for future work is Power et al’s (2021) findings for the nut-cracking chimpanzees of Taï Forest; oil palm phytoliths were “overrepresented” in dietary composition estimates based on analyses of their faeces and dental calculus. These apes access endosperms of oil palm nuts as well as non-palm nuts of Coula and Panda through nut-cracking; it was suggested the spines of the spheroid echinate phytoliths from oil palms could perhaps embed themselves more easily in dental plaque versus phytoliths with a smoother (psilate) surface (Power et al 2021). Such work is vital for continued efforts to create high-resolution dietary comparatives of non-human taxa using phytolith analyses, yet ethnographic comparatives beyond consumption remain lacking – in this case, directed oil palm nut input into sediments associated with nut-cracking tool-use behaviour of western chimpanzees.…”