This monograph argues that biology has a great deal to say that should be of interest to social scientists, historians, philosophers and humanists in general. The author believes that anyone studying the social behaviour of humans must take into consideration both proximate cause - the physiology, biochemistry and social mechanisms of behaviour - and ultimate cause - how the behaviour came to exist in evolutionary time. Goldsmith, a neurobiologist, draws examples from neurobiology, psychology, and ethology (behavioural evolution). The result is a work that attempts to overcome many of the misconceptions that have hindered the contributions that biological sciences have to offer concerning the evolution of human society, behaviour and sense of identity. By re-examining the role of biological explanation in the domain of social development, the author advances a view of human evolution and sheds light on the perennial question of what it means to be human.