The ontogeny of nasal shape: An analysis of sexual dimorphism in a longitudinal sample.

Abstract

Potential integration between the nasal region and noncranial components of the respiratory system has significant implications for understanding determinants of craniofacial variation. There is increasing evidence that sexual dimorphism in body size and associated male-female differences in energetically relevant variables influence the development of the nasal region. To better understand this relationship, we examined the ontogeny of sexual dimorphism in nasal shape using a longitudinal series of lateral cephalograms. We collected a series of two dimensional coordinate landmark data from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations across nine age groups. First, we tested whether there are sex differences in the nasal shape related to ontogenetic increases in body size (i.e., sitting height). Additionally, we examined whether there are male-female differences in patterns of nonallometric variation in nasal shape. Next, we tested whether there are sex differences in the strength of integration between the nasal region and other aspects of the facial skeleton. Our results indicate that there are a number of similarities in patterns of morphological variation in the nasal region between males and females. However, as sitting height increases males exhibit a disproportionate increase in nasal region height that is not present in the female sample. Moreover, the male nasal region is less integrated with the surrounding facial skeleton when compared to the female sample. These results are consistent with the hypothesis that sex differences in nasal development are associated with male-female differences in energetically relevant variables.