Evolving Brains

How did the human brain with all its manifold capacities evolve from basic functions in simple organisms that lived nearly a billion years ago? John Allman addresses this question in Evolving Brains, a provocative study of brain evolution that introduces readers to some of the most exciting developments in science in recent years. Evolving Brains integrates a multiplicity of evolutionary developments involving genetics, response to climate variations, social organization, the nervous system, environment, and behavior. Drawing on a wealth of new findings in molecular genetics and paleontology, Evolving Brains reveals many of the underlying physiological mechanisms that have influenced the formation of our brains. For example, it's no accident that the brain is located near the entrance to the gut because one of the most basic functions of a brain is finding good things to eat and rejecting toxins.

Zooming from the microworld of genes to the macroworld of evolution and behavior, Evolving Brains shows how large brains developed as a buffer against the perilous hazards of an ever-shifting environment, and how the evolution of large brains depended crucially on the formation of the extended family. The rise of the family and its need for communication in turn led to the development of language.

One of the clearest maps yet of the brain's long and eventful journey though time, Evolving Brains reveals a more complete picture of who we are and where we come from.

Given that all organisms share a common ancestry, why is it that they differ so greatly in their capacities to sense, remember, and respond to the world about them? How did we gain our ability to think and to feel? How do we differ from other organisms in these capacities? Our brain endows us with the faculties and the drive to ask these fundamental questions. The answers depend crucially on understanding how brains have evolved. This inquiry into brain evolution is interdisciplinary and multifaceted, based on converging evidence obtained from the study of the genetic regulation of development, the geological history of the earth, and the behavioral ecology of animals, as well as from direct anatomical and physiological studies of brains of animals of different species. From this investigation three themes will emerge: that the essential role of brains is to serve as a buffer against environmental variation; that every evolutionary advance in the nervous system has a cost; and that the development of the brain to the level of complexity we enjoy -- and that makes our lives so rich -- depended on the establishment of the human family as a social and reproductive unit. The author begins by considering one of the basic problems faced by all organisms: how to find food and avoid hazards in a constantly changing world. This leads to the question of how nervous systems detect and integrate the vast array of information available to them and derive from this flood of data adaptive behavioral responses. The evolution of nervous systems depended on a unique mechanism for communication, the action potential, a self-renewing electrical signal that moves along specialized neural fibers called axons that serve as the wires connecting nerve cells. By permitting the development of large nervous systems, this mechanism for neuronal communication made possible the emergence of complex and diverse forms of animal life.