Larger animals have larger brains. However, this does not mean that animals with larger brains are more intelligent than animals with smaller brains. For example, a larger brain is necessary to control larger muscles in larger animals and a larger brain is necessary to process more sensory information from the skin in larger animals. This has nothing to do with intelligence.

During the course of evolution, the brain areas that show the most changes are the cerebral hemispheres (the red areas in the figure): the more recently evolved animals have a larger proportion of the brain taken up by the cerebral cortex. In the ‘higher’ animals (especially the higher mammals), the surface of the cerebral cortex becomes folded. This creates grooves on the surface of the brain called ‘sulci’ (singular = ‘sulcus’). The bumps or ridges on the surface of the brain are called ‘gyri’ (singular = ‘gyrus). The folding of the cortex increases the cortical surface area. The cerebral cortex, made up of four lobes is involved in many complex brain functions including memory, perceptual awareness, thinking, language and consciousness.

Developed initially from work by Eric H Chudler.

Graphics copyright © Eric H Chudler 1996-2004