Brings together research in genetics, behaviour and psychology to provide an understanding of just what it is that makes us human. Dunbar looks at how the human mind has evolved, and draws on his own research during the last five years into the deep psychological and biological bases of music and religion. His theory is based on orders of intentionality: whereas australopithecines barely surpassed the two orders possibly managed by today's apes, H sapiens is capable of five or even six.