Comminution capabilities of extant and fossil anthropoids during molar intercuspation: a preliminary experiment using a chewing simulator / Axelle E. C. Walker

Comminution capabilities of extant and fossil anthropoids during molar intercuspation: a preliminary experiment using a chewing simulator / Axelle E. C. Walker, in colloque "1st Virtual Conference for Women Archaeologists and Paleontologists. Nouveaux apports à l’étude des populations et environnements passés" organisé par le laboratoire Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés (TRACES) de l’Université Toulouse Jean Jaurès et le laboratoire Paléontologie Évolution Paléoécosystèmes (PALEVOPRIM) de l'Université de Poitiers, sous la responsabilité scientifique de Julie Bachellerie, Ana Belén Galán López (Traces), Émilie Berlioz et Margot Louail (Palevoprim). Université Toulouse Jean Jaurès, 8-9 mars 2021. Session 1: Morphological variability, taxonomy and adaptations.

Mammalian teeth and especially molars play a key role in food fragmentation through cyclic dental occlusion during chewing. Mammals fragment food items with various degrees of efficiency depending on their dental morphology. This implies a potential adaptive link between dental morphology and its capability to fragment consumed food items. Understanding dental evolutionary history thus requires to discern which food items, if not all, induce selective pressures on teeth. While molar morphology is expected to influence chewing efficiency and thus the amount of assimilated nutrients, distinct dental occlusal patterns are expected to perform better with particular food items. Testing this hypothesis requires to measure the contribution of the components of chewing and an assessment of chewing efficiency in food fragmentation.Here, we present a preliminary experiment of comminution capabilities in catarrhine primates using a chewing simulator (BeA). This study aims to test the effect of molar morphology during centric occlusion, between phases I and II, i.e. at maximal intercuspation with little or no shearing and grinding, on the comminution of five different food items, which correspond to different mechanical challenges encountered by extant catarrhines in the wild. Using the chewing simulator, we experimentally measure the number of food fragments produced after 5 successive intercuspations in catarrhines displaying different dental occlusal patterns when they consume ductile and tough foods (Procolobus verus, Theropithecus gelada and Gorilla b. graueri) and brittle foods (Homo sapiens).We show that increasing bite force results overall in higher food item degradation, but exceptions are reported notably for ductile and soft foods (apples, gingers and leaves). Intercuspation contributes to the fragmentation of food during the chewing cycle, cusp interlocking fragments brittle and complex food (hazelnuts and crickets). This preliminary experiment sheds light on masticatory capacities of various occlusal patterns in primates and our ability to test these with robotics.