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The Structural Rigidity of the Cranium of Australopithecus africanus: Implications for Diet, Dietary Adaptations, and the Allometry of Feeding Biomechanics
Author(s) -
Strait David S.,
Grosse Ian R.,
Dechow Paul C.,
Smith Amanda L.,
Wang Qian,
Weber Gerhard W.,
Neubauer Simon,
Slice Dennis E.,
Chalk Janine,
Richmond Brian G.,
Lucas Peter W.,
Spencer Mark A.,
Schrein Caitlin,
Wright Barth W.,
Byron Craig,
Ross Callum F.
Publication year - 2010
Publication title -
the anatomical record: advances in integrative anatomy and evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.678
H-Index - 62
eISSN - 1932-8494
pISSN - 1932-8486
DOI - 10.1002/ar.21122
Subject(s) - biting , premolar , bite force quotient , biology , australopithecus , anatomy , allometry , molar , crania , primate , biomechanics , rostrum , mastication , zoology , skull , ecology , paleontology , genus
Abstract Australopithecus africanus is an early hominin (i.e., human relative) believed to exhibit stress‐reducing adaptations in its craniofacial skeleton that may be related to the consumption of resistant food items using its premolar teeth. Finite element analyses simulating molar and premolar biting were used to test the hypothesis that the cranium of A. africanus is structurally more rigid than that of Macaca fascicularis, an Old World monkey that lacks derived australopith facial features. Previously generated finite element models of crania of these species were subjected to isometrically scaled loads, permitting a direct comparison of strain magnitudes. Moreover, strain energy (SE) in the models was compared after results were scaled to account for differences in bone volume and muscle forces. Results indicate that strains in certain skeletal regions below the orbits are higher in M. fascicularis than in A. africanus. Moreover, although premolar bites produce von Mises strains in the rostrum that are elevated relative to those produced by molar biting in both species, rostral strains are much higher in the macaque than in the australopith. These data suggest that at least the midface of A. africanus is more rigid than that of M. fascicularis. Comparisons of SE reveal that the A. africanus cranium is, overall, more rigid than that of M. fascicularis during premolar biting. This is consistent with the hypothesis that this hominin may have periodically consumed large, hard food items. However, the SE data suggest that the A. africanus cranium is marginally less rigid than that of the macaque during molar biting. It is hypothesized that the SE results are being influenced by the allometric scaling of cranial cortical bone thickness. Anat Rec, 293:583–593, 2010. © 2010 Wiley‐Liss, Inc.