Basic research in neuroscience and clinical research on neurological disorders synergistically increase our understanding of the human brain. Traditionally, functional and clinical studies of the human brain were limited to postmortem histology, "natural experiments" (eg, lesions to brain areas caused by trauma or disease), and crude measures of electrical activity such as electroencephalography. More recently, the development of transcranial magnetic stimulation and rapid advances in imaging technology have greatly facilitated human brain research. In rare cases in which treating a neurological disorder involves implanting electrodes, researchers can even record the electrical activity of individual neurons. Although these approaches have led to important insights, they do not allow for a precise dissection of the underlying mechanisms by which the brain mediates perception, cognition, and behavior. Thus, neuroscientists and neurologists remain severely limited in the types of experiments they can perform on human subjects and much of our understanding of brain structure and function is based on research in animal models. In this article, I highlight the enormous potential for synergy between neuroscience and evolutionary biology. Nervous systems have been shaped by evolution, and comparative approaches take advantage of the resulting diversity to gain insight into the neural mechanisms of behavior. On the other hand, nervous systems and the behaviors and perceptions they mediate can play a fundamental role in the evolutionary processes that generate this diversity. To emphasize these points, I describe recent findings from research on African fishes that use electricity to communicate and navigate in their dark underwater world.