Maxillary sinus growth and development in Neanderthals and H. sapiens

We investigate and compare facial and maxillary sinus ontogeny among Neanderthals and H. sapiens to understand the extent of any differences and to investigate if these might arise through differences in developmental interactions. 3D facial and sinus landmarks were acquired from virtual reconstructions of H. sapiens and Neanderthals (H. sapiens N=60, Neanderthals=5). Geometric morphometric analyses compared ontogenetic trajectories of size and shape as well as patterns of covariation among the maxillary sinuses, facial skeleton and its sub-regions. Our results show that facial ontogeny diverges and that maxillary sinuses develop divergently among Neanderthals and modern humans. In both, maxillary sinus, facial and maxillary form are strongly associated. Further, PLS analyses indicate that the ontogeny of maxillary sinus form is strongly associated with that of several facial regions in infancy but becomes most closely associated with the form of the maxilla and nasal cavity in older individuals. In part, this is because the great changes in size that occur in the first few years of life dominate the analyses. However when shape alone is considered a similar shift in patterns of association is observed, albeit with lower correlations indicating that ontogenetic size changes alone do not explain the observed interactions. These findings suggest that despite differences in facial form and ontogenetic trajectories between modern humans and Neanderthals, their maxillary sinuses develop similarly, showing similar patterns of interaction with other facial components, but attaining larger sizes, consistent with the greater space available or expansion provided by the larger maxilla of Neanderthals.