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

Self Cite

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 hothumid environments exhibit turbinate morphologies that minimize air-to-mucosa contact, likely to minimize airflow resistance and/or facilitate expiratory heat-shedding. K E Y W O R D S conchae, human variation, nose, respiratory tract, thermoregulation

Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 55%

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

Marks

Maddux

Butaric

et al. 2019

Self Cite

“…Charles (), Carey and Steegmann (), and Yokley and Franciscus () reported modern humans of European descent to have longer nasal fossae compared to Africans (or Afro‐Americans). Butaric and Klocke () found nasion‐hormion length to be significantly correlated with winter temperature, while Fukase, Ito, and Ishida () demonstrated nasal cavities in prehistoric population of the northern part of the Japanese Archipelago to be longer and taller compared to the early modern Japanese. Importantly, the two latter studies, similarly to ours, were carried out using samples of Asian descent.…”

Section: Discussionmentioning

confidence: 99%

“…Depending on the data available, different Mantel tests slightly differ in terms of the number of populations utilized (see Table ). Partial least‐squares analyses (PLS) between the same sets of variables were carried out as well (see Butaric & Klocke, for details).…”

Section: Methodsmentioning

confidence: 99%

“…It is of note, however, that the study by Maddux et al was based almost solely on external facial dimensions. During the last decade, numerous studies have been carried out to fill this gap (Butaric, ; Butaric & Klocke, ; Butaric & Maddux, ; Butaric, McCarthy, & Broadfield, ; Holton, Yokley, & Butaric, ; Maddux & Butaric, ; Yokley, ; Yokley & Franciscus, ). Nevertheless, our knowledge of the variation of the nasal cavity and paranasal sinuses (including climate‐related variation) is still insufficient, mainly in terms of the number of population samples studied.…”

Section: Introductionmentioning

confidence: 99%

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Nasal cavity and maxillary sinuses form variation among modern humans of Asian descent

Evteev

Grosheva

2019

Objectives: This study explores variation, covariation, and ecogeographic pattern of the nasal cavity, maxillary sinuses, and external midfacial skeleton across 15 populations of east Asian origin inhabiting the Far East, Siberia, Alaska and Greenland. Materials and Methods:We have collected linear measurements of the internal nasal cavity, maxillary sinus and external midfacial skeleton as well as volumes and surface areas of three-dimensional models of the cavity. A set of seven climatic variables, mtDNA and Y-chromosome genetic matrices and a matrix of geographic distances were also utilized.Results: A strong association between form of the nasal cavity and climate was found, whereby all north Asian groups display increased volumes, areas and lengths of the cavity, and surface area to volume ratios (SA/V). Most of Siberian groups exhibit not only large and long, but also wide and tall nasal cavity. The Eskimo-Aleutian speaking groups possess cavities that are vertically short and narrow but of a high SA/V ratio. The sinuses exhibit an exceptionally high level of within-and between-group variation which supports the views on the sinus as an architectural byproduct. Both volume and area of the nasal cavity can be reliably estimated based on a set of simple and repeatable linear measurements.Discussion: While the nasal cavity and maxillary sinus are both larger in a larger facial skeleton, there is a strong inverse relationship between them at a given facial size. Our results do not support the notion that the shape of the internal nasal cavity is more strongly associated with climate compared to the external midfacial morphology.

Common evolutionary patterns in the human nasal region across a worldwide sample

Schroeder

2021

Objectives Variation in the external nasal region among human populations has long been proposed in the literature to reflect adaptations to facilitate thermoregulation, air conditioning, and moisture retention in local climates and environments. More specifically, adaptations in populations living in colder climates have often been assumed due to correlational relationships found between variation in the nasal region and climatic variables. Here, we test this hypothesis by applying a quantitative genetics approach based on the Lande model to assess whether variation in the nasal region can be explained by random neutral processes (e.g., genetic drift) or if non‐random forces (i.e., adaptation) have contributed significantly to its diversity. Materials and methods A mixed‐sex sample representing 28 population groups from Howells' craniometric dataset were analyzed (n = 2504). Twenty standard measurements were chosen to reflect the external skeletal morphology of the nasal region. We apply statistical tests developed from evolutionary quantitative genetics theory to analyze patterns of within‐ and between‐population divergence under a null hypothesis of genetic drift. Results This study finds a rejection of genetic drift in all analyses, across tests that involve all 28 populations, exclusively cold‐climate populations, and with cold‐climate populations excluded, indicating that non‐random evolutionary forces have contributed significantly to variation in the nasal region overall. Discussion These results show that nasal region adaptation is not exclusive to cold‐climate populations, which have often been implicated in the literature to drive nasal variation, instead suggesting that the propensity for adaptation in the nasal region is shared among all human populations.