This book examines the psychology of human behaviour which is dominated by the topic of how the extant behaviour of modern humans may have developed, thus establishing an empirical framework for comprehending human ethology. An aetiology of human behaviour clearly has to be grounded in an understanding of its historical development through time, which is an aspect that has so far not received adequate consideration in scientific literature, be it that of psychology, psychiatry, human evolution, neuroscience, cognitive science, or paleoanthropology. The distinctly interdisciplinary format of this book provides an inkling into the complexity of dealing with human behaviour, and the reasons for its complexity relative to the behaviour of other animal species.