Functional implications of temporal bone pneumatization in hominids

Abstract

Numerous functions have been proposed for the pneumatized spaces of the skull, ranging from acoustic isolation from self‐generated sounds to pressure equalization around the tympanic membrane. By quantifying pneumatized spaces across a number of species it may be possible to elucidate possible functions based on shared morphology and/or phylogenetic history. The purpose of this study was to compare the morphology of pneumatized portions of the temporal bone in extant hominids to determine possible hypotheses about the functions of those spaces.High resolution computed tomography scans of the temporal bone were acquired from humans (N=10), chimpanzees (N=10), gorillas (N=10), and bonobos (N=1). Surface areas and volumes of pneumatized spaces were collected from the entire temporal bone using Amira©. Volumes of interest were cropped from the temporal bone using Quant3D software and analyzed for bone volume fractions, trabecular thickness and anisotropy. These measures were compared according to 1) phylogenetic history and 2) shared craniofacial morphology.Results indicate that the morphology of pneumatized spaces within the hominid temporal bone is not consistently similar or different according to either species membership or shared craniofacial morphology. These findings indicate that the possible functions of pneumatized spaces in the hominid temporal bone are complex and remain elusive.Research supported by NSF (BCS‐052493) and Leakey Foundation.