DARWIN CELEBRATIONS HIGHLIGHT BRAIN EVOLUTION

Understanding patterns of brain evolution also shows us that different lineages have evolved different structural solutions to similar functional problems. Ito and Yamamoto [2009] and Reiner [2009] take us through the forebrains of fishes and birds, respectively, and compare their organization to that of the well-studied mammalian forebrain. Comparative studies of this type may allow us in the future to better understand structure-function relationships between brain and behavior [Smulders, 2009]. The same approach is taken by Amrein and Lipp [2009] to explore the importance of adult neurogenesis in different mammalian species. On the other end of the spectrum, Sol [2009] and Isler and Van Schaik [2009] explore their ideas about the pressures driving the evolution of brain size in birds and mammals, relating them to the possible cognitive advantages on the one hand, and to the constraints of developing large brains on the other hand. And it is of course impossible to understand such constraints without knowing the mechanisms through which developmental processes cause differences in brain size. Striedter and Charvet [2009] compare birds and mammals that have independently evolved large brains, and find similar changes in the proliferative zones of their brains. There are of course many other aspects of brain evolution that are being studied at present. The special feature in Biology Letters was only meant to provide an introduction to this fascinating topic for people who are not familiar with the material. The importance of understanding brain evolution for anyone working in neuroscience cannot be understated [Smulders, As all the readers of Brain, Behavior and Evolution are undoubtedly aware, 2009 was awash with celebrations of Darwin’s bicentenary and the 150th anniversary of the publication of On the Origin of Species . As part of their contribution to these celebrations, Biology Letters published three special features on topics relating to evolution, including one on brain evolution, which was published in February 2009 (vol. 5, issue 1). As the guest editor of this feature, I regarded it as an opportunity to showcase our field of study to the wider biological sciences community. The study of brain evolution is of course a wide and diverse endeavor, from describing and elucidating the patterns of descent with modification over time to thinking about the selective pressures that have shaped nervous systems. Kosik [2009] and Reichert [2009] briefly review the evolution and conservation of the mechanisms involved in synaptic transmission and in brain development, respectively, across many different groups of animals. The findings coming out of this fascinating work elucidate how complicated (molecular) structures and complexes can evolve from simpler ones, because the same molecules can often perform different functions in different contexts. This provides conceptual answers to the kinds of questions raised by Darwin himself about how complex structures like a vertebrate eye could ever have evolved from simpler ancestral structures. In an article associated with (but not in) the special feature, Strausfeld [2009] explores phylogenetic patterns in nervous systems, in this case using them to test hypotheses about the origins of insects.