Mid-Late Pleistocene species are reported to have sinuses of taxonomic and functional interest. Frontal hyperpneumatisation in Homo heidelbergensis is one of few hypothesized autapomorphies of this controversial taxon and Neanderthal sinuses are also said to be distinctively large, resulting from cold adaptation and explaining diagnostic craniofacial morphology. Variation in sinus size within and between populations of recent H. sapiens has been described, but has not been quantified. Sinus variables in Mid-Late Pleistocene hominins were investigated to illuminate causes of craniofacial variation and clarify alpha taxonomy, whilst evaluating theories of sinus function and advancing the understanding of adaptation in this group. Sinus volumes were measured from CT data and geometric morphometric methods were used to identify associated shape variables in a large sample of fossil and extant hominins. Relationships were investigated between these sinus variables and taxonomic/population, dietary, and climatic variables. The results demonstrate that the sinuses have no detectable direct function in Mid-Late Pleistocene hominins but they do respond to selective pressures, such as diet and climate, indirectly via craniofacial adaptation. There is also a relationship with neutral population differences in craniofacial morphology, for at least the frontal sinus. These effects are of varying strength, and it is likely that stochastic development also plays a part in determining differences in individual volumes. Inter-taxon comparisons support frontal hyperpneumatisation as a distinctive, perhaps derived, trait in H. heidelbergensis, but show that H. sapiens has hypopneumatised maxillary sinuses, rather than H. neanderthalensis being hyperpneumatised. Whilst the causes of extremely large sinuses in H. heidelbergensis remain uncertain, small maxillary sinuses in H. sapiens are suggested to result from their derived craniofacial size and morphology. These conclusions build on previous studies to over-turn long-standing but unfounded theories about the pneumatic influences on Neanderthal morphology and the functional nature of sinuses, whilst opening up exciting questions about relationships between strain, climate, pneumatisation, and intraspecific variation.
|Date of Award||2014|
|Supervisor||Ann MacLarnon (Supervisor), Todd Rae (Supervisor) & Chris Stringer (Supervisor)|