The Feeding Biomechanics and Dietary Ecology of Paranthropus boisei

The African Plio‐Pleistocene hominins known as australopiths evolved derived craniodental features frequently interpreted as adaptations for feeding on either hard, or compliant/tough foods. Among australopiths, Paranthropus boisei is the most robust form, exhibiting traits traditionally hypothesized to produce high bite forces efficiently and strengthen the face against feeding stresses. However, recent mechanical analyses imply that P. boisei may not have been an efficient producer of bite force and that robust morphology in primates is not necessarily strong. Here we use an engineering method, finite element analysis, to show that the facial skeleton of P. boisei is structurally strong, exhibits a strain pattern different from that in chimpanzees (Pan troglodytes) and Australopithecus africanus, and efficiently produces high bite force. It has been suggested that P. boisei consumed a diet of compliant/tough foods like grass blades and sedge pith. However, the blunt occlusal topography of this and other species suggests that australopiths are adapted to consume hard foods, perhaps including grass and sedge seeds. A consideration of evolutionary trends in morphology relating to feeding mechanics suggests that food processing behaviors in gracile australopiths evidently were disrupted by environmental change, perhaps contributing to the eventual evolution of Homo and Paranthropus This is the peer reviewed version of the following article: Smith, A. L., Benazzi, S. , Ledogar, J. A., Tamvada, K. , Pryor Smith, L. C., Weber, G. W., Spencer, M. A., Lucas, P. W., Michael, S. , Shekeban, A. , Al‐Fadhalah, K. , Almusallam, A. S., Dechow, P. C., Grosse, I. R., Ross, C. F., Madden, R. H., Richmond, B. G., Wright, B. W., Wang, Q. , Byron, C. , Slice, D. E., Wood, S. , Dzialo, C. , Berthaume, M. A., van, Casteren, A. and Strait, D. S. (2015), The Feeding Biomechanics and Dietary Ecology of Paranthropus boisei, which has been published in final form at https://doi.org/10.1002/ar.23073. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Version

Hard plant tissues do not contribute meaningfully to dental microwear : evolutionary implications

Abstract: Reconstructing diet is critical to understanding hominin adaptations. Isotopic and functional morphological analyses of early hominins are compatible with consumption of hard foods, such as mechanically-protected seeds, but dental microwear analyses are not. The protective shells surrounding seeds are thought to induce complex enamel surface textures characterized by heavy pitting, but these are absent on the teeth of most early hominins. Here we report nanowear experiments showing that the hardest woody shells – the hardest tissues made by dicotyledonous plants – cause very minor damage to enamel but are themselves heavily abraded (worn) in the process. Thus, hard plant tissues do not regularly create pits on enamel surfaces despite high forces clearly being associated with their oral processing. We conclude that hard plant tissues barely inuence microwear textures and the exploitation of seeds from graminoid plants such as grasses and sedges could have formed a critical element in the dietary ecology of hominins