A 3D Geometric Morphometric Analysis of Internal Nasal Fossa Shape Variation in Hot/Cold Climate Populations of Extant Humansтезисы доклада

Дата последнего поиска статьи во внешних источниках: 16 февраля 2016 г.

Работа с тезисами доклада

[1] Nicholas C., Butaric L., Evteev A. A 3d geometric morphometric analysis of internal nasal fossa shape variation in hot/cold climate populations of extant humans // Proceedings of the European Society for the study of Human Evolution 4. — London, 2015. — P. 170–170. Owing to its importance in respiration and thermoregulation, internal nasal cavity shape variation is arguably one of the primary examples of climatic adaptation/selection. The nasal cavity warms inspired air and recoups moisture from exhaled air - both of which are particularly important in cold climates. This has putatively led to the evolution of taller and narrower nasal apertures in cold climate populations of extant humans, as a tall, narrow nose aids in warming inspired air. In warmer climates, warming inspired air is not necessary and wider nasal cavities predominate. This morphology allows for less air resistance when breathing, presumably allowing for greater ease of nasal respiration. Previous studies of nasal shape have either focused on volumetric measurements or have included only a few landmarks in the internal nasal fossa, and more advanced 3D geometric techniques have yet to be applied. Because of this limitation, we do not have an accurate picture of internal nasal fossa shape variation nor how this covaries with external midfacial morphology. In this study, we quantify internal nasal fossa shape using sliding semilandmarks, thus allowing for a more detailed examination of internal nasal shape than has previously been documented in the literature. In order to evaluate ecogeographic variation in internal nasal morphology, we used CT scans of dry crania of individuals from hot (sub-Saharan Africans) and cold (Buriats, Europeans) climates. While we expected that nasal floor shape would covary with climate based on previous literature, the 3D data collection methodology employed here will illuminate more nuanced patterns of nasal fossa shape variation. As such, one of the goals of this study was to develop a method for landmarking the internal nose. Specifically, semilandmark curves were placed along the right side of the internal nasal capsule on our CT scans in the software program Osirix.We chose which slices to landmark by using the landmarks that lie at the junctions between the teeth (i.e., P3/P4, M1/M2, M2/M3), staphylion, and the lowest point on the nasal aperture margin to define vertical planes, as well as using ala to define a horizontal plane. Following digitization, relative warps analysis (RWA) was run on the internal nasal fossa landmarks. Kruskal-Wallis tests run on this data by climate found statistically significant differences between our hot and cold climate groups, as expected. When compared across climate groups, RW1 did not reach significance (p=0.1).However, cold climate populations tend to fall toward the positive end of the range of variation along RW1, showing taller, narrower nasal apertures anteriorly and more horizontally-oriented nasal floors. RW2 shows variation in the superior-inferior positioning of the horizontal landmark curve taken at ala, the relative height/width of the nasal aperture anteriorly, and the region of greatest superior dimensions (whether this point was more anterior or posterior). RW2 was statistically significant (p=0.004), with cold climates correlating again with taller, narrower nasal fossae, in addition to a much more inferiorly located alar landmark curve and more horizontal nasal floors. Interestingly, in our current sample, neither RW1 nor RW2 shows much variation in the shape of the lateral wall of the internal nasal fossa posterior to theM1/M2 junction. These results support prior research regarding variation in nasal floor shape and its relationship to climate. However, this study also points to the fact that a small number of internal nasal landmarks may not be sufficient for characterizing nasal cavity shape. The methods developed for landmarking the internal nasal capsule will allow for future analyses comparing a more detailed analysis of nasal fossa shape with the shape of other internal and external structures, such as the surrounding paranasal sinuses.

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