Sexual dimorphism in the Japanese cranial base: a Fourier-wavelet representation

Area of Science:

• Paleoanthropology
• Biomorphology
• Computational Biology

Background:

• Biological shape analysis often relies on subjective measurements.
• Elliptical Fourier functions (EFFs) provide global shape descriptors.
• Continuous wavelet transforms (CWTs) offer objective localized feature analysis.

Observation:

• A novel computational shape analysis (CSA) approach integrates EFFs and CWTs for comprehensive shape description.
• CSA was applied to lateral radiographic outlines of Japanese cranial bases (CB) from five archaeological periods (n=297).
• Analysis identified statistically significant differences in sex and archaeological age.

Findings:

• Archaeological age differences in CB shape were minor and random, indicating structural stability over time.
• Pronounced and consistent sexual dimorphism was observed in CB shape across all studied periods.
• These dimorphic patterns align with findings in other primate species, suggesting an ancient evolutionary origin.

Implications:

• CSA provides a robust, objective method for quantifying both global and localized features in biological structures.
• The consistent sexual dimorphism in Japanese CB shape supports its role as a reliable indicator of primate evolutionary patterns.
• This approach enhances our understanding of craniofacial evolution and sexual selection in primates.