Asymmetries of cerebellar lobe in the genus homo

Abstract

The endocast was paid great attention in the study of human brain evolution. However, compared to that of the cerebrum, the cerebellar lobe is poorly studied regarding its morphology, function, and evolutionary changes in the process of human evolution. In this study, we define the major axis and four measurements to inspect possible asymmetric patterns within the genus Homo. Results show that significant asymmetry is only observed for the cerebellar length in modern humans and is absent in Homo erectus and Neanderthals. The influence of occipital petalia is obscure due to the small sample size for H. erectus and Neanderthals, while it has a significant influence over the asymmetries of cerebellar height and horizontal orientation in modern humans. Although the length and height of the Neanderthal cerebellum are comparable to that of modern humans, its sagittal orientation is closer to that of H. erectus, which is wider than that of modern humans. The cerebellar morphological difference between Neanderthals and modern humans is suggested to be related to high cognitive activities, such as social factors and language ability.