Teeth as Tools: Preliminary Results of an Experiment using Primate Teeth on Foods

Poster Board Number: 23
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Co-authors:

Amer de Veyra - Western University of Health Sciences; Alvarez Rodriguez, J.C. - Western University of Health Sciences; Daniel Yep - Western University of Health Sciences

Abstract Body :Tooth morphology is a signal of diet in mammals. This is based on established relationships between dental morphology and properties of foods. Comparing the teeth of extinct primates with those of extant primates can, therefore, provide the basis for inference of food properties in extinct diets. Although paleodietary inferences have been made for many extinct primates (including those in our sample), no such study has used an experimental approach like this one. Here, we assume that diet is related to the force required for the molar teeth to masticate the food; thus, molar shape should be adapted to require as little force as possible in altering food by a given amount. Fourteen species of extant primates (tarsier, ten species of strepsirrhine, three species of platyrrhine) were selected. Twelve species of extinct primate were also selected: four adapoids, four omomyids, and four early anthropoids. Lower second molars were 3D printed at a standard length of 2cm (to control for tooth “size”) and fitted to a threaded steel post for mounting in a Lucas Scientific Food Material Properties Tester equipped with a 500N load cell. These “tooth-tools” were used in a modified puncture test to measure the force applied to several samples of five foods, penetrating the foods to approximately the same depth. Food strength and toughness were also measured in these tests. Foods tested were muskmelon, watermelon, apple (Fuji), pear (red Anjou), and banana. Several standard measurements were then made on the teeth using precision calipers for linear dimensions and using water displacement for tooth volume. Regressions of food property results (force, strength, and toughness) on tooth dimensions (sum of shearing crest lengths, cusp/basin height, overall volume) in log space reveal the following. In general, teeth of larger volume require more force to puncture test foods, and perceived strength and toughness of foods are higher for teeth of larger volume. In general, the longer the shearing crests, the less force is required (and perceived strength and toughness are lower), especially for tougher foods (e.g., Fuji apple). In all cases, the coefficient of determination is low-to-moderate, suggesting that any relationship between food performance and tooth dimensions measured here is complex. Future work will include analysis to determine the effect of natural diet in the extant sample, additional foods, and testing of a 1cm set of tooth-tools. Tooth surface files were obtained with permission through MorphoSource (Duke University). 3D printing was carried out by Dr. Juan Garcia (Dept. Art as Applied to Medicine, Johns Hopkins University).