Changing views of brain evolution

Although brain studies began in ancient Egypt, speculations on vertebrate b rain evolution occurred only much later, after the publication of Darwin's Origin of Species in 1859. Subsequently, views of brain evolution have been shaped by a complex interplay of theory and technique. Darwin's theory all owed the variation in brain size and complexity to be reinterpreted within an evolutionary context, albeit an erroneous pre-Darwinian context based on scala naturae. With the development of histological techniques, research s hifted to descriptions of cellular structure, cellular aggregates and their putative interconnections. In spite of these technical advances, brain evo lution continued to be viewed within the context of scala naturae. Followin g the publication of The Comparative Anatomy of the Nervous System of Verte brates by Ariens Kappers, Huber, and Crosby in 1936, there followed a perio d of stasis, after which biological views of evolution were radically alter ed by the confluence of genetics, paleontology, and systematics, termed the Evolutionary Synthesis. Against this background, the development of new ex perimental techniques for establishing neural connections resulted in a new flowering of comparative neuroanatomy. While comparative descriptive and e xperimental studies of brain organization continue, the rapprochement of em bryology and genetics is fueling a new renaissance that promises to increas e our understanding of brain evolution and its genetic basis. (C) 2001 Else vier Science Inc.