Introduction

The human species has a number of uncommon features, one being that we are the only surviving species of our genus Homo. We did have close human relatives such as H. erectus and H. neanderthalensis at one time, and we probably coexisted with both of them before they became extinct. As Ian Tattersall infers, explanations of such an unusual condition might be found through a study of human behaviour and its evolution. As a general principle, behaviour has been a primary factor in all of animal evolution, since it presented organisms with novel conditions of life that influenced their development and physiology. Once mammals acquired the adaptable physiological homeostasis typical of marsupials and placentals, exploratory behaviour exposed them to extreme environments that demanded new behavioural responses, and those ultimately included the ability to change the environment.