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. 2025 Nov;188(3):e70150.
doi: 10.1002/ajpa.70150.

The Anatomical Basis of Skeletal Robusticity in Sex Estimation: Testing the Relationships Between Soft Tissue and Enthesis Size

Jade S De La Paz  1 , Hallie R Buckley  1 , Siân E Halcrow  1   2 , Nawaporn Techataweewan  3 , Stephanie J Woodley  1
Affiliations

The Anatomical Basis of Skeletal Robusticity in Sex Estimation: Testing the Relationships Between Soft Tissue and Enthesis Size

Jade S De La Paz et al. Am J Biol Anthropol. 2025 Nov.

Abstract

Objectives: In skeletal sex estimation, some morphological methods assume relationships between soft tissue (muscle/ligament) size, skeletal robusticity (enthesis size), and sexual dimorphism, where larger muscles theoretically lead to larger entheses (typical male morphology). However, these relationships have not been thoroughly examined. This study assessed these relationships for three skeletal traits used for sex estimation (nuchal crest, mastoid process, rhomboid fossa) and associated soft tissues.

Materials and methods: Muscle size, ligament mass, enthesis surface area, and skeletal sex estimation scores were tested for sex and population differences. This was done through the dissection, three-dimensional scanning, and skeletal analysis of elderly cadavers from New Zealand and Thailand (n = 20).

Results: No population differences were found for muscle or enthesis sizes. Sex differences were observed for all Thai muscle groups, but no New Zealand muscle groups. Sex differences were found for enthesis areas in the New Zealand (1/5) and Thai samples (2/5). Additionally, positive correlations between muscle size and enthesis area (4/10) were found; however, only one of 10 exhibited significant sex differences. Further, morphological sex estimation methods were accurate for both samples, but showed no significant relationships with muscle or enthesis size.

Discussion: These results suggest there may be a relationship between muscle and enthesis size, but there may not be a relationship between muscle size and skeletal robusticity in sex estimation. This research challenges the assumption that this skeletal sexual dimorphism is closely related to soft tissue size, suggesting that larger muscles may not always lead to the robust skeletal traits anthropologists use for sex estimation.

Keywords: New Zealand; Thailand; anthropology; clavicle; cranium; ligaments; muscles; sex estimation; sexual dimorphism; soft tissue attachments.

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