Variation in Paranasal Pneumatisation between Mid-Late Pleistocene Hominins

Abstract

There is considerable variation in mid-late Pleistocene hominin paranasal sinuses, and in some taxa distinctive craniofacial shape has been linked to sinus size. Extreme frontal sinus size has been reported in mid-Pleistocene specimens often classified as Homo heidelbergensis, and Neanderthal sinuses are said to be distinctively large, explaining diagnostic Neanderthal facial shape. Here, the sinuses of fossil hominins attributed to several mid-late Pleistocene taxa were compared to those of recent H. sapiens. The sinuses were investigated to clarify differences in the extent of pneumatisation within this group and the relationship between sinus size and craniofacial variation in hominins from this time period. Frontal and maxillary sinus volumes were measured from CT data, and geometric morphometric methods were used to identify and analyse shape variables associated with sinus volume. Some mid-Pleistocene specimens were found to have extremely large frontal sinuses, supporting previous suggestions that this may be a diagnostic characteristic of this group. Contrary to traditional assertions, however, rather than mid-Pleistocene Homo or Neanderthals having large maxillary sinuses, this study shows that H. sapiens has distinctively small maxillary sinuses. While the causes of large sinuses in mid-Pleistocene Homo remain uncertain, small maxillary sinuses in H. sapiens most likely result from the derived craniofacial morphology that is diagnostic of our species. These conclusions build on previous studies to overturn long-standing but unfounded theories about the pneumatic influences on Neanderthal craniofacial form, whilst opening up questions about the ecological correlates of pneumatisation in hominins.