Personal identification using frontal sinus coding methods: The effect of mixed image modality comparisons.

Several code-based methods have been created for comparing the frontal sinus in skeletal identification scenarios. However, little is known regarding matched-pair accuracy rates of these methods or how varying image modalities may affect these rates. The goals of this study were to validate the exclusion rates and to establish matched-pair accuracy rates of two well-cited coding methods, Cameriere et al. [23] and Tatlisumak et al. [24]. Additionally, individual variables were assessed for consistency in scoring between image modalities. Using a sample of U.S. African American, Native American, and European American females and males (n = 225), we examined individual variable scoring and string codes between two different image modalities (radiographs and CT-based 3D models). Arcades showed poor scoring consistency between modalities (p < 0.001). Although exclusion rates were similar to those reported in the original studies (93%-96%), matched-pair accuracy rates were low (13%-18%). None of the demographics (collection, sex, age, ancestry, and orientation) had an effect on the odds of a match. Interobserver and intraobserver analyses showed moderate to near-perfect agreement for all variables except supraorbital cells, which had minimal to no agreement. Currently, we do not recommend the application of these frontal sinus coding methods independent of other supporting identification methods given low variable consistency and accuracy rates. Visual identification should still be used to include or exclude an identification when using the frontal sinus.

Investigating the relationship between infraorbital canal morphology and maxillary sinus size.

The purpose of the current study was to investigate relationships between maxillary sinus (MS) dimensions and the bony structures associated with the infraorbital nerve (ION). Computed tomographic scans of 87 adult crania (174 sides) from four morphologically diverse groups (West Africans, East Africans, North Asians, Europeans) were utilized. Seven primary variables were collected: infraorbital canal (IOC) type; infraorbital foramen (IOF) shape; distance from the foramen rotundum to IOF (FR-IOF); distance from the posterior wall of the infraorbital groove to IOF (IOG-IOF); and MS length, breadth, and height. Chi-square analyses indicated a significant association between IOC-type and IOF-shape (Pearson chi-square = 12.710; p-value = .013), with the most common pattern being oval IOFs and Type-I IOCs (45.68% of the sample; 74/162 sides). Analysis of covariance indicated a significant effect of ancestry (F = 8.333; p < .001) and MS length (F = 15.406; p < .001) on IOG-IOF distance. Ordinal regression analyses indicated that MS length (Wald chi-square = 7.103; p = .008) also maintained a significant effect on IOC-type, while multinominal regression analyses indicated that none of the measured parameters had a significant effect on IOF-shape. These results have clinical implications: recognizing IOC-type and IOF-shape relative to the MS is important to avoid ION damage during medical procedures. Overall, this study found most individuals possess Type-I IOCs (housed in the maxillary sinus roof) and oval-shaped IOFs. Most aspects of the ION pathway, including IOC-type and IOF-shape, were not influenced by ancestry or sex. However, antero-posteriorly longer MSs tend to possess Type-III IOCs protruding into the sinus, which could lead to surgical complications.

Technical Modifications for the Application of the Total Difference Method for Frontal Sinus Comparison.

Despite being used in personal identification since the 1920s, frontal sinus-based methods are rarely validated. This study is a validation test of the Total Difference Method (TDM). The posterior-anterior radiographs of 10 adults were assessed by two observers using three modes: the Freehand Mode largely followed the original protocols; the Overlay Mode utilized a tracing overlay; and the Semi-Auto Mode used the overlay and macro, walking the user through multiple steps. The modes were evaluated for the time taken to complete each image and the accuracy and repeatability of the line lengths, midline assessment, and angle placement. The repeated measures analysis of variance results for the intra-observer error revealed differences in bias in the angle placement and line length mean error between the rounds and modes. The differences between the rounds were approximately consistent for each mode, suggesting observer error. Significant differences in the inaccuracy of the angle placement and the line lengths between observers by mode were evident; in post hoc testing, the Freehand Mode and Overlay Mode had the greatest error in both variables (p.adj < 0.0001). The Semi-Auto Mode retained no significant error for angle inaccuracy and had the fewest errors for line length inaccuracy (p.adj < 0.01). When using the Semi-Auto Mode, the time was 46.1% faster than that of the Freehand Mode and 34% faster than that of the Overlay Mode (F2,18 = 52.71, p < 0.0001); time slightly improved with method familiarity. The results suggest that the technique required for the TDM can reliably be repeated, and the semi-automated macro improves accuracy and efficiency, but only after the users are familiar with the method and macro procedures. All resources needed to repeat this study are freely available on GitHub.

Ontogenetic patterns in human frontal sinus shape: A longitudinal study using elliptical Fourier analysis.

Frontal sinus morphology is highly variable across individuals, but little is known regarding how or at what age that variation is reached. Existing ontogenetic studies are conflicting and often cross-sectional in nature, limiting understanding of individualistic growth. Studies investigating sinus growth with longitudinal series often focus on lateral cephalograms and consequently do not capture the sinus morphological features that are most relevant to clinical and medicolegal settings (e.g., arcade/scalloping, width-to-height dimensions, asymmetry). Longitudinal analysis of sinus morphology from frontal radiographs is important to understand when sinus morphology stabilizes. The purpose of this study was to investigate at what age the frontal sinus attains its final shape, and whether sex-based differences in ontogeny are evident, using a longitudinal sample of posterior-anterior (PA) frontal radiographs from the AAOF Legacy Collection. Frontal sinus outlines were manually traced in 935 radiographs from 111 individuals (55F/56M) spanning 8-29 years of age. Outlines were subjected to elliptical Fourier analysis (EFA) and underwent principal components analysis (PCA). PC1 (51.02% of variation) appears to represent the relative height and breadth of the sinus, PC2 (11.73%) and PC3 (10.03%) captures the degree of relative complexity in the outlines. Individual PC scores were plotted against age-in-months with individual Loess growth curves. Overall, younger individuals typically display relatively shorter, flatter sinuses, increasing in vertical complexity with age. Mixed-effect models on PC1 indicate significant effects for the repeated measure of years (p < 0.001). Within individuals, Euclidean distances of PCs between each sinus outline and their oldest-age outline (i.e., final morphology) were calculated and plotted against age-in-months with Loess growth curves. The results indicate that final frontal sinus morphology is mostly attained by 20 yoa regardless of sex. There is sexual dimorphism in ontogenetic trajectories: females attain frontal sinus shape earlier than males. Specifically, Loess growth curves of the Euclidean distances to final sinus shape indicate that female shape shows decreased development at 14-16 yoa, with males approaching stabilization at 18-20 yoa. These trends were supported by paired t-tests on PC1 between each year and the oldest age, whereby significant differences end for females starting at 15 and 18 yoa for males. The timing of shape-stabilization in the current study closely aligns with previous studies on linear and size dimensions, indicating a close relationship between the ontogeny of frontal sinus shape and size. This research has several implications in diverse fields. Documenting ontogenetic patterns in modern humans could lead to more accurate interpretations of frontal sinus variation in hominin lineages. Understanding the age at which frontal sinus shape and size stabilizes in pediatric populations has important clinical implications, with future studies needed to investigate if/how sinus development directly relates to sinonasal disease susceptibility (e.g., sinusitis), surgical complications, and/or expected trauma patterns. For forensic practitioners utilizing frontal sinus comparisons for decedent identifications, it is important to know at what age these features stabilize to understand how much change may be expected between antemortem and postmortem radiographs.

The Effects of Cranial Orientation on Forensic Frontal Sinus Identification as Assessed by Outline Analyses.

The utility of frontal sinuses for personal identification is widely recognized, but potential factors affecting its reliability remain uncertain. Deviations in cranial position between antemortem and postmortem radiographs may affect sinus appearance. This study investigates how slight deviations in orientations affect sinus size and outline shape and potentially impact identification. Frontal sinus models were created from CT scans of 21 individuals and digitally oriented to represent three clinically relevant radiographic views. From each standard view, model orientations were deviated at 5° intervals in horizontal, vertical, and diagonal (e.g., left-up) directions (27 orientations per individual). For each orientation, sinus dimensions were obtained, and outline shape was assessed by elliptical Fourier analyses and principal component (PC) analyses. Wilcoxon sign rank tests indicated that sinus breadth remained relatively stable (p > 0.05), while sinus height was significantly affected with vertical deviations (p < 0.006). Mann-Whitney U tests on Euclidean distances from the PC scores indicated consistently lower intra- versus inter-individual distances (p < 0.05). Two of the three orientations maintained perfect (100%) outline identification matches, while the third had a 98% match rate. Smaller and/or discontinuous sinuses were most problematic, and although match rates are high, practitioners should be aware of possible alterations in sinus variables when conducting frontal sinus identifications.

Human maxillary sinus size, shape, and surface area: Implications for structural and functional hypotheses.

OBJECTIVES: Although research into human maxillary sinus (MS) morphology has overwhelmingly focused on sinus volume, other aspects of morphology (e.g., overall shape, mucosal surface area) factor prominently in hypotheses regarding MS form and function. Here, we investigate MS volume in conjunction with measures of MS shape and surface area in a large, diverse sample of modern humans. We test whether variation in MS volume is associated with predictable changes in MS shape (i.e., allometry) and investigate the influence of MS size-shape scaling on mucosal surface area dynamics. MATERIALS AND METHODS: Measures of MS volume and surface area were obtained from computed tomographic (CT) scans of 162 modern human crania from three ancestral backgrounds-Equatorial Africa, Europe, and East Asia. 3D coordinate landmarks and linear measurements were also collected. Multivariate analyses were employed to test for associations between MS volume and other morphological variables. RESULTS: Significant associations between MS volume and 3D shape were identified both across and within the subsamples. Variation in MS volume was found to predominantly relate to differences in MS height and width dimensions relative to MS length. This pattern of allometric scaling was found to differentially influence total mucosal surface area and the SAV ratio. CONCLUSION: This study suggests that variation in MS volume is disproportionately mediated by MS width and height dimensions. This finding has implications for hypotheses which structurally link MS morphology to craniofacial ontogeny and those which suggest that MS morphology may perform adaptive physiological functions.

Ancestry-based variation in maxillary sinus anatomy: Implications for health disparities in sinonasal disease.

Paranasal sinus drainage is mediated by mucociliary transport and gravity. However, human orthograde posture, along with the superior positioning of the maxillary sinus (MS) ostium, increases reliance on the mucociliary system. Previous research has thus suggested that differences in MS size and shape may impede mucociliary clearance, potentially contributing to disparities in sinusitis susceptibility. To further investigate this hypothesis, this study collected 29 three-dimensional (3D) coordinate landmarks and seven linear measurements of MS morphology from 167 computed tomography (CT) scans of crania of European, East Asian, or Equatorial African ancestry. MANOVA results reveal the Asian-derived individuals are characterized by both a significantly taller MS (F = 14.15, p < 0.0001) and a significantly greater distance from the MS floor to the ostium (F = 17.22, p < 0.0001) compared to those of European and African ancestry. A canonical variate (CV) analysis conducted on 3D landmark data provides corroborative results, distinguishing Asian-derived individuals predominantly on the basis of a relatively lower MS floor. As a greater distance between the MS floor and ostium may impede mucociliary clearance, our results suggest MS anatomy may be a more prominent factor in chronic sinusitis among individuals of Asian ancestry compared to those of European and African ancestries. This provides tentative evidence of an anatomical etiology for chronic sinusitis even in the absence of anatomical variants/abnormalities (e.g., nasal polyps, concha bullosa, Haller's cells, and Agger nasi cells). Further research into the relationship between MS anatomy and sinusitis, in addition to socioeconomic inequalities of healthcare, is warranted to continue evaluating possible contributions to health disparities.

Ontogenetic variation in human nasal morphology.

Internal nasal cavity morphology has long been thought to reflect respiratory pressures related to heating and humidifying inspired air. Yet, despite the widely recognized importance of ontogeny in understanding climatic and thermoregulatory adaptations, most research on nasal variation in modern and fossil humans focuses on static adult morphology. This study utilizes cross-sectional CT data of three morphologically distinct samples (African, European, Arctic) spanning from infancy to adulthood (total n = 321). Eighteen landmarks capturing external and internal regions of the face and nose were subjected to generalized Procrustes and form-space principal component analyses (separately conducted on global and individual samples) to ascertain when adult-specific nasal morphology emerges during ontogeny. Across the global sample, PC1 (67.18% of the variation) tracks age-related size changes regardless of ancestry, while PC2 (6.86%) differentiates between the ancestral groups irrespective of age. Growth curves tracking morphological changes by age-in-years indicate comparable growth trajectories across all three samples, with the majority of nasal size and shape established early in ontogeny (<5 years of age). Sex-based trends are also evident, with females exhibiting a more truncated growth period than males, particularly for nasal height dimensions. Differences are also evident between the anterior and posterior nose, with the height and breadth dimensions of the anterior nasal aperture and nasal cavity showing differential ontogenetic patterns compared to the choanae. Cumulatively, these results suggest that multiple selective pressures influence human nasal morphology through ontogenetic processes, including metabolic demands for sufficient oxygen intake and climatic demands for adequate intranasal air conditioning.

Respiratory adaptation to climate in modern humans and Upper Palaeolithic individuals from Sungir and Mladec.

As our human ancestors migrated into Eurasia, they faced a considerably harsher climate, but the extent to which human cranial morphology has adapted to this climate is still debated. In particular, it remains unclear when such facial adaptations arose in human populations. Here, we explore climate-associated features of face shape in a worldwide modern human sample using 3D geometric morphometrics and a novel application of reduced rank regression. Based on these data, we assess climate adaptations in two crucial Upper Palaeolithic human fossils, Sungir and Mladec, associated with a boreal-to-temperate climate. We found several aspects of facial shape, especially the relative dimensions of the external nose, internal nose and maxillary sinuses, that are strongly associated with temperature and humidity, even after accounting for autocorrelation due to geographical proximity of populations. For these features, both fossils revealed adaptations to a dry environment, with Sungir being strongly associated with cold temperatures and Mladec with warm-to-hot temperatures. These results suggest relatively quick adaptative rates of facial morphology in Upper Palaeolithic Europe.

Revisiting global patterns of frontal sinus aplasia utilizing computed tomography.

While frontal sinus aplasia (agenesis, absence) has been proposed as a potential marker in forensic positive identifications, frequency rates are likely dependent upon how presence is defined. This study investigates how two methods of defining frontal sinus presence affects aplasia frequency rates. Using CT scans of 772 adult individuals from diverse geographic regions, frontal sinus presence was assessed two ways: 1) the XR-method- coded present if the sinus extended above the supra-orbital line, and 2) the CT-method- coded present with any indication of the frontal sinus. The XR-method consistently provided higher aplasia frequencies, averaging an 18.31% discrepancy with the CT-method. Method discrepancies were higher in females (averaged-sides: 24.6%) than males (averaged-sides: 13.82%). Oceanian individuals displayed the highest aplasia rates using either method, and the highest discrepancy between methods (averaged-sides: 31.30%); Europeans, displaying the lowest aplasia rates in either method, also displayed the lowest method discrepancy (average-sides: 7.37%). Fisher's Exact tests on the biologically-defined CT aplasia rates indicate females are significantly different from males for unilateral aplasia (p=0.0035); Arctic populations are significantly different from most groups (all p<0.005), exception being Oceanian. Results suggest the lower, biologically-defined CT aplasia rates are more useful in corroborating identifications than the inflated XR frequencies and illustrate the importance of citing aplasia rates from similarly-composed samples. However, due to practicality and resource availability, the XR-method may be more appropriate. Most importantly, reported aplasia rates from one method should be cited in casework utilizing the other method.

Anatomical Sciences Education Among Biological Anthropology Graduates: a Solution to the Dearth of Anatomy Educators?

The need for anatomical knowledge is increasingly in demand as new medical and allied-health professions programs continue to open, but there is a growing dearth of educators with formal training in the anatomical sciences. Several sources for anatomy faculty have been suggested, including surgeons, but few have considered a more obvious, alternative approach to this shortage: hiring qualified faculty from other PhD departments/programs whose graduates receive formal training in anatomy, including biological anthropologists. This study surveyed 305 biological anthropology graduates to assimilate information about the nature and extent of training among biological anthropology graduates in the core anatomy disciplines (anatomy, histology, embryology, histology, neuroanatomy), and to determine whether biological anthropology graduates value and apply anatomy training. Only 36% of PhDs reported that anatomy was a required course, but 72% of PhD graduates took an anatomy course (usually gross anatomy with a human cadaveric dissection laboratory). Histology, embryology, and neuroanatomy also were not required to obtain a PhD, though some of this material was covered during the anatomy course, and some students opted to take these courses as electives. Forty-five percent of PhD students reported teaching experience in gross anatomy courses with cadaveric dissection. Ninety-four percent of biological anthropology PhD graduates are prepared to teach human osteology, and 48% are comfortable teaching gross anatomy. Biological anthropology graduates bring unique expertise, training, and research experience to medical education programs, and many are well-suited to fill the growing number of anatomy faculty positions.

Climatic adaptation in human inferior nasal turbinate morphology: Evidence from Arctic and equatorial populations.

OBJECTIVES: The nasal turbinates directly influence the overall size, shape, and surface area of the nasal passages, and thus contribute to intranasal heat and moisture exchange. However, unlike the encapsulating walls of the nasal cavity, ecogeographic variation in nasal turbinate morphology among humans has not yet been established. Here we investigate variation in inferior nasal turbinate morphology in two populations from climatically extreme environments. MATERIALS AND METHODS: Twenty-three linear measurements of the inferior turbinate, nasal cavity walls, and airway passages were collected from CT scans of indigenous modern human crania from Equatorial Africa (n = 35) and the Arctic Circle (n = 35). MANOVA and ANCOVA were employed to test for predicted regional and sex differences in morphology between the samples. RESULTS: Significant morphological differences were identified between the two regional samples, with no evidence of significant sexual dimorphism or region-sex interaction effect. Individuals from the Arctic Circle possessed superoinferiorly and mediolaterally larger inferior turbinates compared to Equatorial Africans. In conjunction with the surrounding nasal cavity walls, these differences in turbinate morphology produced airway dimensions that were both consistent with functional expectations and more regionally distinct than either skeletal component independently. CONCLUSION: This study documents the existence of ecogeographic variation in human nasal turbinate morphology reflecting climate-mediated evolutionary demands on intranasal heat and moisture exchange. Humans adapted to cold-dry environments exhibit turbinate morphologies that enhance contact between respired air and nasal mucosa to facilitate respiratory air conditioning. Conversely, humans adapted to hot-humid environments exhibit turbinate morphologies that minimize air-to-mucosa contact, likely to minimize airflow resistance and/or facilitate expiratory heat-shedding.

Anatomical Variation in Maxillary Sinus Ostium Positioning: Implications for Nasal-Sinus Disease.

Among humans, superiorly located maxillary sinus ostia (MSO) result in drainage complications and maxillary sinus (MS) disease. While previous studies investigate maxillary sinusitis frequency or MSO-position relative to specific nasal landmarks, few explore MSO-position to overall MS dimensions. This study investigates whether MSO-position relates to MS size/shape and if sex-based differences exist. Twenty-nine landmarks, placed on magnetic resonance images (MRIs) of 109 individuals (males = 57; females = 52), captured maximum dimensions of the cranium, MS, nasal cavity, and MSO-position relative to the MS floor (MSO_MSF) and nasal floor (MSO_NCF). Landmark coordinates were used to calculate centroid sizes and 13 linear distances; distances were size standardized by cranial centroid-size. Principal components analysis (PCA) on 3D-coordinates indicates that variation in MSO-position relates to superior-inferior MS positioning within the face (PC1 22% variance) and MS height (PC2 12% variance). Regression analyses indicate that MS size (r2 = 0.502; P < 0.001) and height (r2 = 0.589; P < 0.0001) strongly contribute to MSO_MSF: larger, taller MSs exhibit greater MSO_MSFs. Sex-based differences were not evident in PC shape-analyses nor among size-standardized dimensions. However, Mann-Whitney U-tests indicate females have absolutely smaller MSs (P = 0.001) and MSO_MSF distances (P = 0.001). Further, regressions indicate females exhibit lower MSO_MSFs for a similar MS height. Overall, MSOs superiorly placed relative to the MS floor correlate with larger, taller MSs and/or sinuses positioned inferiorly within the face. While craniofacial surgeons/clinicians should be aware of potential sex-based differences in MS size and MSO position, this study does not suggest that higher incidences of female-reported sinusitis relate to sex-based differences in MS anatomy. Anat Rec, 302:917-930, 2019. © 2018 Wiley Periodicals, Inc.

Nasal variation in relation to high-altitude adaptations among Tibetans and Andeans.

OBJECTIVES: High-altitude (>2500 m) populations face several pressures, including hypoxia and cold-dry air, resulting in greater respiratory demand to obtain more oxygen and condition inspired air. While cardiovascular and pulmonary adaptations to high-altitude hypoxia have been extensively studied, adaptations of upper-respiratory structures, e.g., nasal cavity, remain untested. This study investigates whether nasal morphology presents adaptations to hypoxic (larger noses) and/or cold-dry (tall/narrow noses) conditions among high-altitude samples. METHODS: CT scans of two high- and four low-altitude samples from diverse climates were collected (n = 130): high-altitude Tibetans and Peruvians; low-altitude Peruvians, Southern Chinese (temperate), Mongolian-Buriats (cold-dry), and Southeast Asians (hot-wet). Facial and nasal distances were calculated from 3D landmarks placed on digitally-modeled crania. Temperature, precipitation, and barometric pressure data were also obtained. RESULTS: Principal components analysis and analyses of variance primarily indicate size-related differences among the cold-dry (Mongolian-Buriats) and hot-wet (Southeast Asians) adapted groups. Two-block partial least squares (PLS) analysis show weak relationships between size-standardized nasal dimensions and environmental variables. However, among PLS1 (85.90% of covariance), Tibetans display relatively larger nasal cavities related to lower temperatures and barometric pressure; regression analyses also indicate high-altitude Tibetans possess relatively larger internal nasal breadths and heights for their facial size. CONCLUSIONS: Overall, nasal differences relate to climate among the cold-dry and hot-wet groups. Specific nasal adaptations were not identified among either Peruvian group, perhaps due to their relatively recent migration history and population structure. However, high-altitude Tibetans seem to exhibit a compromise in nasal morphology, serving in increased oxygen uptake, and air-conditioning processes.

A call for action: Why anthropologists can (and should) join the discussion on climate change through education.

Anthropologists, human biologists, and researchers in related fields have been investigating the human-environment interaction and its effects on health for decades. While there have been numerous studies from the medical- and health-sectors pointing to the connection between climate change and health needs, as well as studies advocating for the incorporation of appropriate curricula addressing these needs in medical schools and health-professional programs, this connection is not being systematically taught to our future healthcare professionals. Here, we first briefly summarize research highlighting the interaction between environment and health; we follow this with discussion about why this interaction is important for current and future medical professionals to understand, particularly in light of the current issues of climate change. We specifically address how anthropologists and human biologists have contributed to the literature on marginal environments and climate change, and how anthropological research may be incorporated in health-oriented and medical classrooms to aid in this discussion. Through interdisciplinary collaboration between anthropologists, human biologists, medical-health professionals, and researchers in other fields, we can learn from our past and play a part in piecing together our future health care issues and needs.

Zygomaticomaxillary Morphology and Maxillary Sinus Form and Function: How Spatial Constraints Influence Pneumatization Patterns among Modern Humans.

Previous research has suggested that the maxillary sinuses may act as "zones of accommodation" for the nasal region, minimizing the impact of climatic-related changes in nasal cavity breadth on surrounding skeletal structures. However, a recent study among modern human crania has identified that, in addition to nasal cavity breadth, sinus morphology also tracks lateral facial form, especially anterior-posterior positioning of the zygomatics. Here, we expand upon this previous study to further investigate these covariation patterns by employing three samples with distinct combinations of nasal and zygomatic morphologies: Northern Asians (n = 28); sub-Saharan Africans (n = 30); and Europeans (n = 29). For each cranium, 30 landmarks were digitized from CT-rendered models and subsequently assigned to either a midfacial or maxillary sinus "block." Two block partial least squares (2B-PLS) analyses indicate that sinus morphology primarily reflects superior-inferior dimensions of the midface, rather than either nasal cavity breadth or zygomatic position. Specifically, individuals with relatively tall midfacial skeletons exhibit more inferiorly and laterally expanded sinuses compared to those with shorter midfaces. Further, separate across-group and within-group 2B-PLS analyses indicate that regional differences between samples primarily build upon a common pattern of midfacial and sinus covariation already present within each regional group. Allometry, while present, only explains a small portion of the midface-sinus covariation pattern. We conclude that previous findings of larger maxillary sinuses among cold-adapted individuals are not predominantly due to possession of relatively narrow nasal cavities, but to greater maxillary and zygomatic heights. Implications for sinus function and midfacial ontogeny are discussed. Anat Rec, 300:209-225, 2017. © 2016 Wiley Periodicals, Inc.

Ecogeographic variation across morphofunctional units of the human nose.

OBJECTIVES: Although the internal nose is overwhelmingly responsible for heat and moisture exchange during respiration, external nasal morphology is more commonly cited as evincing climatic adaptation in humans. Here, we assess variation across all four morphofunctional units of the complete nasorespiratory tract (external pyramid, nasal aperture, internal nasal fossa, and nasopharynx) to determine which units provide the strongest evidence of climatic adaptation. MATERIALS AND METHODS: We employ 20 linear measurements collected on 837 modern human crania from major geographic (Arctic Circle, Asia, Australia, Europe, Africa) and climatic (polar, temperate, hot-arid, tropical) zones. In conjunction with associated climatic and geographic data, these morphological data are employed in multivariate analyses to evaluate the associations between each of these functional nasal units and climate. RESULTS: The external pyramid and nasopharynx exhibit virtually no evidence of climate-mediated morphology across the regional samples, while apparent associations between climate and nasal aperture morphology appear influenced by the geographic (and likely genetic) proximities of certain populations. Only the internal nasal fossa exhibits an ecogeographic distribution consistent with climatic adaptation, with crania from colder and/or drier environments displaying internal nasal fossae that are longer, taller, and narrower (especially superiorly) compared to those from hotter and more humid environments. CONCLUSIONS: Our study indicates that the internal nasal fossa exhibits a stronger association with climate compared to other aspects of the human nose. Further, our study supports suggestions that regional variation in internal nasal fossa morphology reflects demands for heat and moisture exchange via adjustment of internal nasal airway dimensions. Our study thus provides empirical support for theoretical assertions related to nasorespiratory function, with important implications for understanding human nasal evolution.

Morphological Covariation between the Maxillary Sinus and Midfacial Skeleton among Sub-Saharan and Circumpolar Modern Humans.

OBJECTIVES: Maxillary sinus volume tracks ecogeographic differences in nasal form and may serve as a zone of accommodation for ontogenetic and evolutionary changes in nasal cavity breadth. However, little is known regarding how sinus volume is distributed within the midface. This study investigates morphological covariation between midfacial and sinus shape to better understand structural and functional relationships between the sinus, midface, and nasal cavity. METHODS: Cranial and sinus models were rendered from CT scans of modern human samples from two disparate climates: sub-Saharan (South Africans [n = 15], West Africans [n = 17]), and circumpolar (Siberian Buriats [n = 18], Alaskan Inuit [n = 20]). Twenty-five 3D coordinate landmarks were placed on the models and subjected to generalized Procrustes analysis. Two-block partial least squares (2B-PLS) analysis was employed to identify patterns of covariation. RESULTS: The 2B-PLS analysis indicates PLS1 (58.6% total covariation) relates to height and breadth relationships between the midface, nasal cavity, and maxillary sinus. Significant regional differences in PLS1 scores are evident: circumpolar samples possess taller/narrower noses with taller/wider sinuses compared to sub-Saharan samples. Importantly, PLS1 indicates that sinus breadth is not exclusively related to nasal cavity breadth; variation in lateral sinus expansion toward the zygoma represents an important contributing factor. PLS2 (16%) relates to supero-inferior positioning of the sinus within the midface. Allometric trends, while statistically significant, explain only a small portion of these covariation patterns. CONCLUSIONS: These results suggest that the maxillary sinus serves as a zone of accommodation at the confluence of multiple facial components, potentially minimizing effects of morphological alterations to certain components on adjacent structures. Am J Phys Anthropol 160:483-497, 2016. © 2016 Wiley Periodicals, Inc.

Differential Scaling Patterns in Maxillary Sinus Volume and Nasal Cavity Breadth Among Modern Humans.

Among modern humans, nasal cavity size and shape reflect its vital role in air conditioning processes. The ability for the nasal cavity to augment its shape, particularly in inferior breadth, likely relates to the surrounding maxillary sinuses acting as zones of accommodation. However, much is still unknown regarding how nasal and sinus morphology relate to each other and to overall craniofacial form, particularly across diverse populations with varying respiratory demands. As such, this study uses computed tomographic (CT) scans of modern human crania (N = 171) from nine different localities to investigate ecogeographic differences in (1) the interaction between maxillary sinus volume (MSV) and nasal cavity breadth (NCB) and (2) scaling patterns of MSV and NCB in relation to craniofacial size. Reduced major axis (RMA) regression reveals that all samples exhibit an inverse relationship between MSV and NCB, but statistical significance and the strength of that relationship is sample dependent. Individuals from cold-dry climates have larger MSVs with narrower NCBs, while smaller MSVs are associated with wider NCBs in hot-humid climates. MSV and NCB each scale with positive allometry relative to overall craniofacial size. However, sample differences are evident in the both the interaction between MSV and NCB, as well as their correlation with craniofacial size. While these results provide further support that the maxillary sinus and nasal cavity are integrated among populations from opposite ends of the climatic spectrum, additional epigenetic factors are needed to explain variation of these structures among populations from more intermediate climates.

A preliminary 3D computed tomography study of the human maxillary sinus and nasal cavity.

Despite centuries of investigation, the function of the maxillary sinus (MS) and underlying patterns governing its form remain elusive. In this study, we articulate a methodology for collecting volumetric data for the MS and nasal cavity (NC) from computed tomography (CT) scans and report details for a small sample of 39 dried human crania of known ecogeographic provenience useful for assessing variation in MS size and shape. We use scaling analyses to preliminarily test the hypothesis that volumes of the nasal cavity (NCV) and maxillary sinus (MSV) are inversely correlated such that the NC covaries with size of the face, whereas the MS "fills in" the leftover space [proposed by Shea: Am J Phys Anthropol 47 (1977):289-300]. Against expectation, MSV is not significantly correlated with NCV or any cranial size variable. NCV, on the other hand, scales isometrically with facial size. The results of this pilot study suggest that NCV covaries with facial size, but that the MS does not simply fill in the leftover space in the face. The role, if any, of the MSs in midfacial function and architecture remains unclear. Larger sample sizes, additional environmental variables, and assessment of MS and NC shape are necessary to resolve this issue.