Climatic Effects on the Nasal Complex: A CT Imaging, Comparative Anatomical, and Morphometric Investigation of Macaca mulatta and Macaca fascicularis

Abstract

Previous studies exploring the effects of climate on the nasal region have largely focused on external craniofacial linear parameters, using dry crania of modern human populations. This investigation augments traditional craniofacial morphometrics with internal linear and volumetric measures of the anatomic units comprising the nasal complex (i.e., internal nasal cavity depth, maxillary sinus volumes). The study focuses on macaques (i.e., Macaca mulatta and Macaca fascicularis) living at high and low altitudes, rather than on humans, since the short residency of migratory human populations may preclude using them as reliable models to test the long-term relationship of climate to nasal morphology. It is hypothesized that there will be significant differences in nasal complex morphology among macaques inhabiting different climates. This study integrated three different approaches: CT imaging, comparative anatomy, and morphometrics-in an effort to better understand the morphological structure and adaptive nature of the nasal complex. Results showed statistically significant differences when subsets of splanchnocranial and neurocranial variables were regressed against total maxillary sinus volume for particular taxa. For example, basion-hormion was significant for M. fascicularis, whereas choanal dimensions were significant only for M. mulatta. Both taxa revealed strong correlation between sinus volume and prosthion to staphylion distance, which essentially represents the length of the nasal cavity floor-and is by extension an indicator of the air conditioning capacity of the nasal region. These results clearly show that climatic effects play a major role in shaping the anatomy of the nasal complex in closely related species. The major influence upon these differing structures appears to be related to respiratory-related adaptations subserving differing climatic factors. In addition, the interdependence of the paranasal sinuses with other parts of the complex strongly indicates a functional role for them in nasal complex/upper respiratory functions.

Climate Signatures in the Morphological Differentiation of Worldwide Modern Human Populations

“…However, it has been observed that Neanderthal facial and especially nasal morphology does not necessarily match expected climatic patterns seen among modern human populations, and is sometimes described as a ''paradox'' (e.g., Holton and Franciscus, 2008; though see Márquez and Laitman, 2008 for an example of wide nasal apertures in cold climates in macaques). Alternative explanations for the evolution of the Neanderthal face have focused on functional demands associated with paramasticatory activities (e.g., Rak, 1986;Trinkaus, 1987) or on random genetic drift (e.g., Howell, 1952;Hublin, 1998) as driving forces.…”

Three‐Dimensional Geometric Morphometric Analysis of the Nasopharyngeal Boundaries and Its Functional Integration with the Face and External Basicranium Among Extant Hominoids

“…Prognathism is measured here between prosthion and staphylion. This distance has been used as a measure of palate length (Ashton, ; Laitman et al, ) and nasal cavity length (Marquez and Laitman, ). Marquez and Laitman () have also found a relationship between piriform aperture width and prosthion–staphylion length, suggesting that this measure bears a strong functional morphologic relationship to URT proportions.…”

Comparative morphology of porpoise (Cetacea: Phocoenidae) pterygoid sinuses: Phylogenetic and functional implications

“…Reidenberg and Laitman (2008) refer to the system as “pterygoid sacs.” However, in keeping with terminology used by previous workers who define the air sinus system as an extension of the middle ear cavity (Fraser and Purves, 1960; Mead and Fordyce, 2009), and because it is entirely contained within bone medially and connective tissue and venous plexuses laterally and ventrally, this study refers to the ventral air sinus system as a whole, and the pterygoid sinus and associated diverticula as “sinuses.” The air sinus system is assumed to be a cetacean synapomorphy because the entire paranasal sinus complex was lost in the process of the telescoping of the skull and corresponding “flattening” of the maxillae and frontal bones (Reidenberg and Laitman, 2008; Mead and Fordyce, 2009). The exact homologies of the sinuses have not been comprehensively studied; however, Murie (1873) noted that the cetacean pterygoid sinus may be homologous with the maxillary, frontal, and sphenoidal sinuses of terrestrial mammals, while Kellogg (1936) proposed homology between the pterygoid sinuses and the lateral diverticula of the pharynx found in many ungulates. Mead and Fordyce (2009) suggest that some cranial foramina in living cetaceans are vestigial and possibly associated with the paranasal sinuses.…”