Functional craniology and brain evolution

Abstract

Anatomy and morphometrics have been experiencing a new renaissance in recent decades due to the new techniques and computed methodology used in imaging and statistics. Following this revolution, anatomical systems are currently analyzed by investigating the relationships among their components, in ontogeny and phylogeny. Accordingly, evolution is no more interpreted in terms of single and independent traits, but through integrated patterns and more comprehensive processes. In this sense, paleoneurology should be interpreted as the study of the relationships between brain and braincase during evolution. Morphogenesis is based on the functional and structural relationships between soft and hard tissues. The bones of the braincase, the cerebral cortex, the vascular networks, the connective layers and the cerebrospinal fluid constitute a balanced morphogenetic complex which constrains and influences evolutionary changes. Within this network, the brain largely shapes the bones in the upper endocranial areas, while in the lower endocranial areas the reverse relationship is more likely, due to constraints associated with the facial block and with the cranial base. Most of the spatial changes described in hominid paleoneurology are associated with the fronto-parietal lateral expansion of the endocranial volumes, and modern humans display a further dilation of the whole parietal surface. The study of endocasts can only provide information on size and shape changes associated with the neurocranial morphology, and fields like histology and neuroanatomy are necessary to support robust evolutionary hypotheses. Integration with neuropsychology and other biomedical fields is furthermore necessary to evaluate possible relationships between brain spatial organization and functional topics, such as metabolism or cognition.