Jon Kaas started his talk by showing some of the main differences between the monkey and human brain. Moving further back in evolution, he continued by outlining the organization of the tiny brains of some of the earliest mammals. Further along the line, Australopithecine brains were about one third the size of ours. Modern molecular genetic methods yielded a full tree of mammalian evolution, allowing for a detailed study of brain evolution in mammals. Early mammals (e.g., the Tenrec Echinops telfairi) only have a very small neocortex with only few functional areas. Tree shrews (Tupaia glis) have considerably increased neocortex with a wide variety of functional subunits, in particular a substantially enlarged visual system. Early primates such as prosimians also show the expansion of visual cortex. However, in addition to the retained complex visual system, now these animals have already a much more elaborate, greatly expanded motor and premotor cortex, compared to earlier animals. These motor areas can activate ethologically relevant complex behaviors when stimulated in the fully anesthetized animals. Humans have much larger brains, which lead to modularization and hemispheric specialization in order to avoid the connectivity problems associated with the larger distances between brain areas.
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