Exploring age-related variations during calcaneal growth

Methods for age estimation in juvenile osteological samples are highly accurate compared to those of adults, but little is known about the variation of the foot bones during growth. This study explores the age-related morphological changes of the calcaneus, which is often well preserved even in the case of multiple or damaged burials, using Geometric Morphometric Methods. A sample of 33 modern human juvenile calcanei (known age/sex= 22; unknown sex/age= 11) was 3D scanned using an Artec3D Space Scanner. 5 age categories (0-15 years) were defined; unknown sex/age specimens were classified as ND. A template of 15 landmarks and 209 semi-landmarks was applied to the digital models. The (semi)landmark configurations were superimposed by Generalized Procrustes Analysis. A form space Principal Component Analysis (PCA) was computed using the known sample to explore variation during growth, while ND specimens were projected within it. The analysis shows that PC1 (ca. 93%) is highly correlated with size and accounts for ontogenetic allometry. Negative scores (youngest individuals) are characterized by a compact morphology while positive scores (oldest individuals) show both a greater definition of the sustentaculum talii and sinus tarsii and more pronounced edges for the talar and cuboid articular facets. The projected sample follows the trajectory of the known sample, which means that our ND specimens can be aged in the 5 categories after being projected. Our results suggest that age-related morphological changes of the calcaneus during growth may be used to estimate the general age of juvenile skeletal remains.