Endocranial integration and modularity in an adult human sample with known age and sex

Cranial endocasts represent a key proxy for reconstructing brain morphology in human evolution. Despite major advances in virtual anthropology and geometric morphometrics, patterns of endocranial integration and modularity as well as their variation with sex and age remain poorly explored. In this study, we apply 3D geometric morphometrics and multivariate analyses, including a surface-based mapping of local integration, to a sample of 115 modern human endocasts to detect patterns of morphological integration and variations linked to sex and age. Five bilateral endocranial modules, corresponding to major brain regions (frontal, parietal, temporal, occipital lobes, and cerebellum), were defined. Our results reveal a strong covariation across endocranial modules, with the highest covariation observed between the frontoparietal region and between the occipital and cerebellar region. Sexual dimorphism is mostly exhibited in endocranial volume, whereas age-relates variation is associated with significant regional changes, particularly in the frontal region, without clear evidence of volumetric reduction. These findings provide new insights into endocranial integration and modularity, highlighting the value of endocast for investigating brain morphology, variation, and ageing in humans and across their evolutionary history.