Pelvic morphology and body size in relation to the preauricular sulcus: Evidence from medieval to modern Iberia

The preauricular sulcus has long been debated as a pelvic feature variably attributed to obstetric stress, ligamentous traction, and broader biomechanical processes. To clarify its determinants, we analyzed 409 adult individuals from three archeological and one early modern skeletal collection from the Iberian Peninsula, integrating graded sulcus expression with pelvic morphology, body size, and demographic context. Sulcus expression shows marked sexual dimorphism: females exhibit the full morphological spectrum, whereas males display limited variation and are overwhelmingly concentrated in the lowest grades. Hierarchical log-linear models and ordinal logistic regression analyses indicate that preauricular sulcus presence is not associated with stature, body mass, or overall pelvic canal dimensions. Instead, inferior pelvic dimensions, particularly pubic length and outlet measures, emerge as the only consistent morphological predictors, with significant sex-specific interactions restricted to the outlet. Neither population affiliation nor age at death modifies the association between sex and sulcus expression. Taken together, these results support a model in which the preauricular sulcus reflects sex-specific biomechanical environments of the inferior pelvis rather than overall body size or population-level variation. Within this framework, sulcus development is best interpreted as ligament-mediated remodeling shaped by localized mechanical loading and hormonally mediated changes associated with pregnancy, while remaining robust across diverse biocultural contexts and mortality regimes.