A brief introduction to the principles of neurobiology from an evolutionary perspective -- from single-celled organisms to complex invertebrates such as flies -- ideal for use as supplemental textbook. Greenspan presents the mechanisms that allow behavior to become ever more sophisticated -- from simple avoidance behavior of Paramecium through to the complex cognitive behaviors of the honeybee -- and shows how these mechanisms produce the increasing neural complexity found in these organisms. The book ends with a discussion of what is universal about nervous systems and what may be required, neurobiologically, to be human.