The evolution of the primate cerebellum

Investigations into the evolution of the primate brain have consistently focussed on the neocortex as the principal area of change. New evidence is presented here to show that the cerebellum has also shown significant expansion over primate brain evolution indicating that exclusive focus on the neocortex is unwarranted. More detailed analysis shows that individual components of the cerebellar-neocortical system have undergone correlated evolution independently of change in the rest of the brain, providing support for the theory of mosaic evolution. Among primates, the great ape cerebellum is shown to be particularly large, indicating that this area of the brain is more important in great apes than in other primates. Possible ecological, social, developmental and motor correlates are investigated with the aim of accounting for cerebellar expansion. Implications for previous theories of primate brain evolution are discussed.