Evidence for precuneus expansion in recent human evolution

Abstract

The evolution of neurocranial morphology in our species is characterized by bulging of the parietal region, a feature unique to Homo sapiens. In modern humans, expansion of the parietal surface occurs during the first year of life, and this expansion is absent in chimpanzees and Neandertals. Similar variation in brain shape among living adult humans is associated with expansion of the precuneus. Using MRI-derived structural brain templates, we compare medial brain morphology between humans and chimpanzees through shape analysis and geometrical modeling. We find that the main medial brain morphological difference is a prominent expansion of the precuneus in our species. The precuneus is a major hub of brain organization, a central node of the default-mode network, and plays an essential role in visuospatial integration. Together, the comparative neuroanatomical and paleontological evidence suggest that a conspicuous enlargement of the precuneus is a specialization of Homo sapiens that evolved in the last 150,000 years and that may explain the evolution of recent human cognitive specializations.