Evolution of the Vertebrate Brain

Abstract

The term biological evolution commonly denotes a history of the traits and relationships (phylogeny) of organisms, as well as the processes that underlie that history. Although vertebrates and their brains have existed for at least 500 million years, most of our knowledge regarding the changes in brains and the processes that have produced these changes has been derived from the patterns of variation exhibited by the brains of living vertebrates. This has been necessarily true because brains, like most other soft structures, do not fossilize, and little information can be gleaned from endocranial casts beyond the relative size and external shape of the brains of extinct vertebrates.