The ontogeny of nasal floor shape variation in extant humans

Abstract

Variation in nasal floor topography has generated both neontological and paleontological interest. Three categories of nasal floor shape (Franciscus: J Hum Evol 44 (2003) 699-727) have been used when analyzing this trait in extant humans and fossil Homo: flat, sloped, and depressed (or "bi-level"). Variation in the frequency of these configurations within and among extant and fossil humans has been well-documented (Franciscus: J Hum Evol 44 (2003) 699-727; Wu et al.: Anthropol Sci 120 (2012) 217-226). However, variation in this trait in Homo has been observed primarily in adults, with comparatively small subadult sample sizes and/or large age gradients that may not sufficiently track key ontogenetic changes. In this study, we investigate the ontogeny of nasal floor shape in a relatively large cross-sectional age sample of extant humans (n = 382) ranging from 4.0 months fetal to 21 years post-natal. Results indicate that no fetal or young infant individuals possess a depressed nasal floor, and that a depressed nasal floor, when present (ca. 21% of the sample), does not occur until 3.0 years postnatal. A canonical variates analysis of maxillary shape revealed that individuals with depressed nasal floors were also characterized by relatively taller anterior alveolar regions. This suggests that palate remodeling at about 3.0-3.5 years after birth, under the influence of tooth development, strongly influences nasal floor variation, and that various aspects of dental development, including larger crown/root size, may contribute to the development of a depressed nasal floor. These results in extant humans may help explain the high frequency of this trait found in Neandertal and other archaic Homo maxillae.

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

“…Further, Smith et al () suggest that pneumatization into particular processes may be limited to certain developmental windows, during which lack of spatial availability may permanently restrict future sinus expansion. Importantly, several studies on regional variation in human facial ontogeny (Viðarsdóttir et al, ; Viðarsdóttir and O'Higgins, ; Sardi and Rozzi, ; Nicholas and Franciscus, ; Freidline et al, ) have shown that differences in basic spatial dynamics seen in adult facial morphology appear early during ontogeny. Accordingly, our results may suggest that adult humans with large (i.e., tall) zygomaticomaxillary interfaces possess sinuses that extend further into the zygomatic process of the maxilla (or even into the zygomatic) because these individuals possess sufficient space for pneumatization to occur in the area during particular periods of their growth and development.…”

Fetal and neonatal maxillary ontogeny in extant humans and the utility of prenatal maxillary morphology in predicting ancestral affiliation

“…The current study confirms the results of work by Mooney & Siegel (1986a,b) and Weinberg et al (2005) that showed population variation in maxillary traits developing, in some cases, prenatally. While not all maxillary traits that vary by population follow this pattern (such as the internal nasal floor, see Nicholas & Franciscus, 2014), there is sufficient shape variation at these young ages for it to be easily quantified using a relatively restricted set of coordinate landmarks. Geometric morphometric methods' ability to quantify continuous variation, along with variation that may be more difficult to parse due to the physically small size of fetal material, may help to increase accuracy when trying to estimate ancestry for fetal or neonatal individuals.…”

Occipital hemi‐bun development and shape covariation in a longitudinal extant human growth sample

“…Generalized Procrustes analysis (GPA) was performed to translate, rotate, and scale the landmark configurations of each subject (Mitteroecker, Gunz, Windhager, & Schaefer, ; Rohlf & Slice, ). The role of allometry was assessed by regressing all Procrustes‐aligned shape coordinates on centroid size (Adams, Collyer, & Sherratt, ; Drake & Klingenberg, ; Mitteroecker et al, ; Nicholas & Franciscus, ). This process allowed an assessment of the statistical relationship between shape and size within each age point.…”