Entheseal variation and locomotor behavior during growth

Entheses are acknowledged as skeletal markers capable of revealing several biological and behavioral aspects of past individuals and populations. However, entheseal changes (ECs) of juvenile individuals have not yet been studied with a systematic approach. This contribution aims at investigating the morphological changes occurring at the femoral insertion of the gluteus maximus and tibial origin of the soleus muscles to highlight a potential link between the morphological features of those entheses and skeletal maturity in relation to sex, age, and locomotor developmental patterns. The sample consisted of 119 skeletons (age-at-death: 0-30 years) belonging to the Documented Human Skeletal Collection of the Certosa Cemetery (Bologna, Italy). The entheseal variation during the last stages of skeletal maturation in young adults was assessed using existing recording standards. A recording protocol for each enthesis was developed for immature individuals to subdivide the morphological variability into discrete categories. Univariate, bivariate, and multivariate statistical analyses were performed to investigate the variation of entheseal morphologies and measurements in relation to bone metrics, degree of epiphyseal closure, sex, age, and locomotor developmental patterns. A statistically significant relationship was observed between ECs morphological patterns and age for both entheses, while sexual differences were negligible. A relationship between ECs morphological pattern and locomotor milestones emerged only for the gluteus maximus. Even though further testing is needed on other documented skeletal collections, our protocol could be usefully applied in forensic and archaeological fields and serving as important reference for evolutionary investigations.