Thesis (MMus (Music))--University of Stellenbosch, 2009. / The evolutionary origins of music, defined as “an intentional action in which complex, learned vocalizations (and/or instrumentally produced sound) are combined with the movement of the body in synchrony to a beat” is investigated through an appraisal of the musilanguage theory and relevant literature. The biological adaptations allowing the production and perception of music are identified and their evolutionary histories investigated. The critical adaptations that made rhythmical body movement possible evolved around 1.6 million years ago. These include habitual bipedalism and changes in the vestibular system. There is almost no fossil evidence to inform on the timing and nature of the complex, learned vocalization. However, that the thoracic vertebrate canal had modern proportions by 600 000 years ago indicates that archaic humans were able to achieve the respiratory control necessary to sing. The size of this canal is a proxy for the number of nerve cells that control respiration via the intercostal and abdominal muscles. Musicality is essential to the human mind. Infants are born with rudimentary musical skills with regard to melody, temporal sequences and vocal and bodily imitation. These capabilities are central to the newborns’ innate ability to elicit care by synchronizing their vocal and bodily actions with that of the caregivers. Musical rhythm is further used to entrain bodily and neural oscillations and this permit the creation of trust and social bonding. It is concluded that protomusic developed between 1.6 million and 600 000 years ago. Protomusic consisted of entrained rhythmical whole body movements initially combined with grunt-like vocalizations. The evidence investigated cannot be used to infer the origins of modern music. KEYWORDS: Music, Evolution, Synchronisation, Melody, Dance, Bipedality, Vestibular system, Thoracic vertebrate canal, Infant-directed communication, Neural entrainment

Entrainment is the rhythmic coordination of movement with a signal or other person. Most studies on entrainment have looked at synchronization with auditory or visual signals, whereas much less is known about how entrainment emerges mutually between individuals, especially when they are in physical contact with one another. In this dissertation, I empirically explored dance partnering as an ecological model for understanding interpersonal entrainment through haptic interaction. I began by performing a statistical meta-analysis of functional neuroimaging articles devoted to the most common experimental paradigm for entrainment, namely externally-paced finger tapping to an acoustic rhythmic stimulus (Chapter 2). The results showed that the cerebellar vermis was a strong neural marker of entrainment, as it was more activated by externally-paced tapping than by self-paced tapping, whereas the basal ganglia was activated by both types of rhythmic movements. Next, I used functional magnetic resonance imaging (fMRI) with a group of participants trained at couple dancing in order to explore the neural basis of haptic mutual entrainment, with a focus on the dynamics of leading and following (Chapter 3). While mutual interaction overall engaged brain networks involved in somatosensation, internal-body sensation and social cognition, leading showed enhanced activity principally in areas for motor control and self-initiated action, whereas following showed enhanced activity mainly in sensory and social-cognition areas. Finally, I used 3D motion capture to explore multisensory coupling for mutual entrainment at the group level during folk dancing (Chapter 4). The results showed that dancers relied most extensively on haptic coupling to synchronize as a group, whereas auditory and visual coupling were dependent on the spatiotemporal context. These studies advance our understanding of the neural and behavioural mechanisms underlying joint actions in which entrainment emerges mutually through haptic interaction. / Thesis / Doctor of Philosophy (PhD) / Entrainment is the rhythmic coordination of movement with a signal or other person. Most studies on entrainment have looked at synchronization with auditory or visual signals, whereas much less is known about how entrainment emerges mutually between individuals, especially when they are in physical contact with one another. I began my research by performing a statistical analysis of the literature examining the brain basis of synchronization with auditory signals, identifying a key brain area for entrainment. Next, using a group of participants trained at couple dancing, I explored the brain areas engaged when two individuals in physical contact improvised movement together, focusing on who is leading or following the interaction. Finally, I explored how folk dancers use multiple sensory signals (auditory, visual and tactile) to synchronize as a group. These studies advance our understanding of the neural and behavioural mechanisms by which people mutually entrain through physical interaction.