This study investigates ontogenetic changes in human scapular morphology using three-dimensional geometric morphometrics with whole-bone and region-specific analyses. The aim is to evaluate whether the scapula follows a regular developmental pattern and whether its functionally distinct components, the scapular spine (SS) and glenoid fossa (SGF), exhibit divergent growth trajectories indicative of modular development. This approach assesses interactions between global and local morphological change and explores the influence of size, biomechanics, and ossification timing on scapular development. We analyzed 3D surface scans of 127 scapulae from non-adult and adult individuals from the medieval San Pablo Collection, Spain, and the documented Lisbon Collection, Portugal. Seven ontogenetic groups were defined using dental and chronological age. Landmark and semi landmark configurations were generated for the entire scapula, the scapular spine, and the glenoid fossa. Shape and form variation were examined using Generalized Procrustes Analysis and Principal Component Analysis. Across all regions, PC1 captured the main axis of ontogenetic variation, separating age groups in both shape and form space. Whole-scapula analyses revealed a gradual developmental pattern, whereas regional analyses highlighted distinct trajectories. The scapular spine showed progressive curvature and torsion, likely reflecting muscular loading, while the glenoid fossa displayed more constrained changes linked to joint stabilization and ossification timing. These findings support a modular model of scapular growth, with regions responding to intrinsic developmental processes and extrinsic biomechanical influences. Integrating regional and whole-bone analyses reveals developmental plasticity not detectable through global approaches alone, with implications for forensic, clinical, paleoanthropological, and bioarchaeological research.
