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Dental topographic analysis is a suite of measurements designed to capture functional information about occlusal morphology that can be effectively applied to wear series. Recent studies have revealed that some primate folivores exhibit an apparent improvement in dental function (i.e., increased occlusal sharpness) with increased wear—a phenomenon termed ‘dental sculpting.’ While dental sculpting has been identified in a folivorous platyrrhine (Alouatta) and colobine (Presbytis), its prevalence across primate phylogeny and ecomorphology remains underexplored. A wear series of 13 bonobo (Pan paniscus) second mandibular molars were analyzed for dental topography and amount of wear. 3D surfaces were generated in Avizo from μCT data of specimens housed at the Royal Belgian Institute of Natural Sciences representing the broadest range of wear states available. Occlusal sharpness was measured as convex Dirichlet normal energy (DNE) using the R package molaR. Wear was quantified as the dentine exposure ratio (DER) by imaging specimens in occlusal view and measuring the ratio of exposed dentine area to total occlusal area. Linear regression analysis found that DNE declined significantly with increased DER (p= 0.002), with moderate explanatory power (r2= 0.555). These findings suggest that dental sculpting does not occur in Pan paniscus. Our results contrast with those found for the frugivorous platyrrhines Ateles and Plecturocebus, who maintain DNE with wear. Rather, they indicate that bonobos lack compensatory mechanisms to preserve occlusal sharpness across their lifespans and underscore the importance of nutrition gained through relatively soft dietary materials that do not require significant cutting or slicing to efficiently consume.
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Changes in molar topography and 3D shear crest lengths with tooth wear in two cercopithecid primates from Malaysia
As herbivorous, diphyodont mammals with relatively low-crowned molars, primates experience changes in dental function during their lifetimes as teeth become progressively worn. Maintaining tooth function with wear is thought to pose a particular challenge for folivorous primates whose diets emphasize molar shearing actions. Recent studies using dental topographic methods suggest that certain primate folivores have molar morphology that maintains or increases functional shearing surfaces with tooth wear (‘dental sculpting’). Evidence for this phenomenon has been found in folivorous but not frugivorous New World monkeys, supporting the hypothesis that dental sculpting is an adaptive trait linked to diet. This analysis extends these methods to two sympatric Old World monkeys from Sabah, Malaysia, possessing distinct diets and dental morphologies: the folivorous colobine Trachypithecus cristatus (n=25) and the more frugivorous cercopithecine Macaca fascicularis (n=22). For each species, 3D shear crest lengths and four dental topographic variables (relief index, slope, angularity, and Dirichlet Normal Energy [DNE]) were measured from variably worn lower second molars. Preliminary results indicate that for any given degree of wear, Trachypithecus has longer shear crest lengths and higher relief, slope, angularity, and DNE than Macaca. The two species exhibit different patterns and degrees of change in topography and shearing crest lengths across the wear series. However, these changes do not always match expectations based on their respective diets. Correlations between 3D shear crest lengths and other dental topographic measurements suggests that the type of metric used to assess shearing potential may affect whether or not dental sculpting is detected.
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- Award ID(s):
- 1846153
- PAR ID:
- 10148503
- Date Published:
- Journal Name:
- American Journal of Physical Anthropology
- Volume:
- 171
- Issue:
- S69
- ISSN:
- 0002-9483
- Page Range / eLocation ID:
- 164
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Relationships between sex, body mass and tooth wear in Cayo Santiago rhesus monkeys (Macaca mulatta)null (Ed.)Understanding factors affecting tooth wear in primates is of interest because as teeth wear, their chewing efficiency can change—in some species positively and in others negatively. It is well known that teeth wear with age, but relationships between sex and tooth wear and between body size and tooth wear are less well understood. Here we analyze molar wear scores from a cross-sectional sample of 212 Cayo Santiago rhesus monkey (Macaca mulatta) adults examined in 1985. Because males are generally larger than females --potentially processing more food over their lifetimes--we hypothesized that with age included in an ordinal logistic regression model, males would exhibit significantly greater wear than females. We further hypothesized that males of larger body mass would exhibit greater wear than males of smaller body mass. Finally, because many of the females were pregnant or lactating at the time of dental examination, we hypothesized that there would be no relationship between body mass and wear in females. We found that with age included in ordinal logistic regression models, males had significantly more worn molars than females, larger males had more worn molars than smaller males, and that for females, molar wear was not significantly related to body mass. These results suggest that over the life course, animals with larger body sizes (males vs. females and larger vs. smaller males) may accumulate more wear than those with smaller body sizes. Future analyses to be conducted on the Cayo Santiago monkeys’ skeletal remains will further evaluate this possibility. Funding Sources: The Cayo Santiago colony is supported by NIH 5P40OD012217. This project is supported by NSF grants to DG-S., LK., MZ, and QW (NSF #1926528, 1926481, 1926402, and 1926601).more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/ajpa.24023
