A Step Forward in Encephalization: The Virtual Endocast of the Middle Pleistocene Hominin from Ceprano, Italy

The Ceprano calvaria from central Italy (∼400 ka) offers crucial insights into human evolution during the Middle Pleistocene. Despite its relatively late age, when derived Neanderthal-like specimens already existed in Europe, Ceprano retains a remarkably plesiomorphic morphology. This article focuses on the endocranial anatomy of Ceprano, aiming to clarify its place within the process of brain reorganization in the genus Homo during the Middle Pleistocene.

We conducted analyses on both the original and retrodeformed reconstructions of the specimen, considering that the shape of the Ceprano's endocast may be influenced by taphonomic distortion. This dual approach is particularly relevant in endocranial studies, as retrodeformation may be problematic in removing meaningful information, such as cerebral asymmetries. Additionally, a cladistic analysis employing 34 discrete endocranial characters was conducted.

Our data confirmed that Ceprano exhibits an endocranial capacity of 1,165 mL, placing it at the threshold between Homo erectus sensu lato and more encephalized human taxa. Both geometric morphometrics and discrete trait analyses reveal an intermediate condition, blending a low, platycephalic morphology with volumetric expansion and signs of cortical reorganization. Consistently, the cladistic approach points out that Ceprano represents the sister taxon to all Middle and Late Pleistocene encephalized hominins.

Therefore, we suggest that Ceprano should be considered a proxy for the ancestral morphology of Homo heidelbergensis, involving a two-phase model of brain evolution, in which an overall cerebral enlargement preceded lineage-specific cortical reorganizations. Thus, its mosaic morphology highlights the neuroanatomical foundations preceding subsequent divergences within later Homo species.