1Anthropology, University of Massachusetts Amherst, 2Geology and Anthropology, University of Cincinnati, 3Anatomy, The Geisel School of Medicine at Dartmouth, 4Anthropology, Dartmouth College, 5Biology, University of Massachusetts Amherst
Thursday 4:45-5:00, Ballroom C
Despite its bearing robust facial features and dental proportional convergences with robust australopiths, Hadropithecus was likely not a hard-object feeder. Stable isotopes (δ13C and δ15N) show a match for CAM plants such as Alluaudia but not for hard-seeded C3 plants or C4 grasses. Heavy predation on Alluaudia leaves might help explain this plant’s own spiny defenses and other craniodental features of Hadropithecus (small gape, low relative enamel thickness, high molar occlusal surface complexity). Finite element analysis shows that Hadropithecus’ skull was not as strong as that of the closely related hard-object feeder, Archaeolemur, but that Hadropithecus could (1) transfer muscle to bite force at P4 and especially M2 with greater mechanical advantage, and (2) produce absolutely higher bite forces. However, bite force divided by tooth occlusal area is 10-30% higher in Archaeolemur. Thus, despite the high mechanical advantage of its feeding apparatus, Hadropithecus produced lower bite force per unit occlusal area than did Archaeolemur and was structurally weaker. The hominin likenesses of Hadropithecus may be related to increased mechanical efficiency of its hypertrophied cheek teeth (P4-M3), possibly signaling high-bulk feeding on low “quality” foods.
Our point, that hominin craniodental likenesses do not necessarily translate into high bite forces per unit occlusal area, is not meant to imply that Paranthropus did not consume hard objects, or indeed that Paranthropus and Hadropithecus had similar diets. Rather, we suggest that their craniodental likenesses may reflect the ability of both to process high-bulk, low-quality foods.
FEA analysis supported by NSF DBI-0743460 to E.R. Dumont and I.R. Grosse. Isotope research supported by the UC Laboratory Fee Research Programme (09-LR-07-115818-DOMN to B.E. Crowley and N.J. Dominy) and a Guggenheim Fellowship (L.R. Godfrey).