Sex Based Variation in Ear Morphology in a Nigerian Population: Anthropological Classification

Abstract

Aims: This study investigated the morphological characteristics of the external ear in a Nigerian population, with emphasis on sex-based variation in categorical traits and continuous anthropometric measurements, and explored their biometric and forensic implications. Study Design: A cross-sectional anthropometric study was conducted among adult Nigerians, comprising 118 males and 57 females. Participants were opportunistically recruited, resulting in unequal sex representation across the sample. Place and Duration of Study: Ear samples were collected from Zaria, Ado Ekiti, Isuochi, and Owerri, Nigeria, between October 2025 and May 2026. Methodology: A cross-sectional study was conducted among 175 Nigerian adults. Morphological traits (lobule type, helix shape, concha type, and tragus prominence) and continuous measurements (ear length, ear width, and lobule length) were recorded. Frequency distributions were computed, chi-square tests assessed categorical associations with sex, independent t-tests compared continuous traits, and principal component analysis (PCA) explored multivariate clustering. Effect sizes (Cramér’s V and Cohen’s d) and 95% confidence intervals were reported. Results: The most prevalent features observed were free lobules (59.4%), continuous helix (96.0%), triangular concha (47.1%), and prominent tragus (86.3%). Chi-square analysis identified significant associations between sex and both lobule type (χ² = 15.91, p = 0.00035, Cramér’s V = 0.29) and concha type (χ² = 21.09, p < 0.001, Cramér’s V = 0.34). In contrast, no significant associations were found for helix shape or tragus prominence. Independent t-tests indicated that lobule length differed significantly between sexes (mean difference = -1.30 cm, 95% CI: -1.65 to -0.96 cm, p < 0.0001, Cohen’s d = -1.11), while ear length and width did not show significant differences. Principal component analysis (PCA) confirmed that lobule length was the primary contributor to sex differentiation, with PC1 and PC2 describing over 86% of the total variance, showing that ear width and lobule length are the most significant traits in determining ear morphology. Conclusion: The study establishes that lobule type, concha type, and lobule length are reliable indicators of sexual dimorphism in Nigerians, with lobule length showing a large effect size. These findings enrich anthropological datasets, emphasise population-specific traits such as triangular concha, and affirm the forensic and biometric potential of ear morphology.