Archaeological evidence for musical activities pre-dates even the earliest-known cave art and it remains the case that no human culture has yet been encountered that does not practise some recognisably musical activity. Yet the human abilities to make and appreciate music have been described as "amongst the most mysterious with which [we are] endowed" (Charles Darwin, 1872) and music itself as "the supreme mystery of the science of man" (Claude Levi-Strauss, 1970). Like language, music has been the subject of keen investigation across a great diversity of fields, from neuroscience and psychology, to ethnography, to studies of its structures in its own dedicated field, musicology; unlike the evolution of human language abilities, it is only recently that the origins of musical capacities have begun to receive dedicated attention. It is increasingly clear that human musical abilities are fundamentally related to other important human abilities, yet much remains mysterious about this ubiquitous human phenomenon, not least its prehistoric origins. It is evident that no single field of investigation can address the wide range of issues relevant to answering the question of music's origins. This review brings together evidence from a wide range of anthropological and human sciences, including palaeoanthropology, archaeology, neuroscience, primatology and developmental psychology, in an attempt to elucidate the nature of the foundations of music, how they have evolved, and how they are related to capabilities underlying other important human behaviours. It is proposed that at their most fundamental level musical behaviours (including both vocalisation and dance) are forms of deliberate metrically-organised gesture, and constitute a specialised use of systems dedicated to the expression and comprehension of social and emotional information between individuals. The abilities underlying these behaviours are selectively advantageous themselves; in addition, various mechanisms by which the practice of musical activities themselves could be advantageous are outlined.