A cross-population study of sexual dimorphism in the bony labyrinth

Abstract

Previous research found sexual dimorphism in the bony labyrinth of a Greek population sample (Osipov et al. 2013). This study intends to investigate the nature of this structure’s sexual dimorphism across populations of diverse geographic origin and to identify the effect of inter-population variation on the accuracy of determining sex using the bony labyrinth. Three population samples of known sex were analyzed originating from Europe (n = 30), Africa (n = 38), and North America (n = 30). The discriminant function developed in Osipov et al. (2013) was applied, and new function equations for sex estimation were developed. In addition, we used principal component analyses for investigating population differences, while bivariate tests were used to compare across population samples, sexes, and anatomical sides. A significant level of sexual dimorphism was found in all population samples, being driven by both size and shape differences. Discriminant functions for sex estimation were developed for all three population samples combined (71.4% accuracy) as well as separately (70–80% accuracy). The German sample was the least sexually dimorphic, whereas the North American sample exhibited the greatest sexual dimorphism. The size and shape of the bony labyrinth also significantly differed across population samples. The bony labyrinth is found to be sexually dimorphic across distinct population groups. Due to significant differences across our population samples, the accuracy of the previously proposed method for sex determination (Osipov et al., 2013) was relatively low. For this purpose, this study presented new functions, whose accuracy was tested in three distinct population samples.

Sexing the bony labyrinth: A morphometric investigation in a subadult and adult Belgian identified sample

“…Yet, this traditional osteometric method makes it difficult to isolate size and to differentiate shape variables which depend directly on size (allometry) from those that are function of other factors such as sex. The sexual dimorphism highlighted in the present study possibly reflects the differences of size and body mass that exist between males and females [29,34,44], which vary among human populations [41,43], more than pure shape differences by sex. To further explore modalities of sexual dimorphism of the bony labyrinth using a geometric morphometric approach could be valuable.…”

“…European populations (continental vs. insular) [41,43]. Yet, comparisons are somewhat restricted because of differences in measurement sets and acquisition protocols (Table 7).…”

“…The univariate and multivariate discriminant functions established achieved respective rates of classification accuracy of 75% and 82.4%. Uhl et al recently tested Osipov's multivariate function 1 separately on three different populations (North-American, German and Zulu) and found lower accuracy levels (from 66.6% to 73.3%) [43]. Yet, in both studies some of the linear and angular measurements defined by Spoor and Zonneveld were not considered and, more importantly, subadult sexual dimorphism of the bony labyrinth was not examined.…”

The influence of subsistence strategy and climate on bony labyrinth morphology in recentHomo sapiens

“…Groups were scanned at several resolutions with several X-ray CT scanners across numerous institutions (Baab et al, 2018;Copes, 2012;Uhl et al, 2016Uhl et al, , 2020Ward et al, 2020). Scan resolution for these data is available in Table 3.…”

“…This equation was applied by Uhl et al (2016), but recent work shows that the equation does not work on all groups and again calls the existence of labyrinthine sexual dimorphism into question (Ward et al, 2020). Uhl et al (2020) reported that the levels of sexual dimorphism and bony labyrinth morphology differed across diverse population samples.…”