The study of mental evolution began with Charles Darwin’s 1872 publication “The Expressions of Emotions in Man and Animals” and was continued by Romanes in publications dated 1883 and 1888. However, there was a poor scientific understanding of human behavior and the mind in the late 19th century. Today, thanks to more than a century of rigorous psychological research on human behavior and the workings of the mind—and the added knowledge of paleontology, archaeology, anthropology, and history—mental evolution is accepted today by most scientists. Joseph Altman adds a new dimension to this knowledge by linking research on vertebrate brain and behavior to our current understanding of the human brain. Many of the structures in the human brain are shared with vertebrates–going as far back as fish on the phylogenetic scale. Altman calls these relationships “legacies.” We have a fish legacy, a reptilian legacy, a mammalian legacy, and a primate legacy preserved in our brain structures and in our behavior patterns. This book offers a unique view of the neuroscientific foundations for understanding human nature.