The craniomandibular mechanics of being human

Abstract

Diminished bite force has been considered a defining feature of modern Homo sapiens, an interpretation inferred from the application of two-dimensional lever mechanics and the relative gracility of the human masticatory musculature and skull. This conclusion has various implications with regard to the evolution of human feeding behaviour. However, human dental anatomy suggests a capacity to withstand high loads and two-dimensional lever models greatly simplify muscle architecture, yielding less accurate results than threedimensional modelling using multiple lines of action. Here, to our knowledge, in the most comprehensive three-dimensional finite element analysis performed to date for any taxon, we ask whether the traditional view that the bite of H. sapiens is weak and the skull too gracile to sustain high bite forces is supported. We further introduce a new method for reconstructing incomplete fossil material. Our findings show that the human masticatory apparatus is highly efficient, capable of producing a relatively powerful bite using low muscle forces. Thus, relative to other members of the superfamily Hominoidea, humans can achieve relatively high bite forces, while overall stresses are reduced. Our findings resolve apparently discordant lines of evidence, i.e. the presence of teeth well adapted to sustain high loads within a lightweight cranium and mandible.

Moa diet fits the bill: virtual reconstruction incorporating mummified remains and prediction of biomechanical performance in avian giants

“…R. Soc. B 283: 20152043 previously published procedures [37,38,41,58]. All FEMs were homogeneous and tet4 elements were isotropic.…”

“…As this is a comparative study, the stress results are only of value in this context (i.e. it is relative stress magnitudes that are important, not actual values) [34,38,40]. General protocols applied in this study have been applied and validated previously [38].…”

“…it is relative stress magnitudes that are important, not actual values) [34,38,40]. General protocols applied in this study have been applied and validated previously [38]. Principal component (PC) axes were used to create phylomorphospaces following Sidlauskas [66] in the Rhetenor module of the software MESQUITE [67].…”

“…We compare these with two extant ratites with different feeding behaviours and diets, the emu (Dromaius novaehollandiae) and southern cassowary (Casuarius casuarius) [33]. FEA is a computer-based engineering technique that has been used widely in comparative biomechanics [34,35] and has previously been used to infer diet in living and extinct taxa, including birds [36][37][38][39][40][41]. Here we ask (i) whether there are variations in the magnitudes and distributions of stress in ratite skulls under specific loading conditions, and (ii) whether these are indicative of different feeding behaviours and diets among moa and extant ratites.…”

Middle Pliocene hominin diversity: Australopithecus deyiremeda and Kenyanthropus platyops

“…Apart from postcanine dental size, this study particularly highlights morphological characters used to assess the loading of the masticatory system, including the position of the zygomatic process, variations in the length of the anterior and postcanine dental rows, and the height of maxilla [18][19][20][21][22]. Hence, dietary adaptation is a prime candidate as the key to understanding morphological diversity between the three species, although random genetic drift could play as much a role as selection [23].…”