Darwin has pioneered the functional perspective in the study of emotions which currently dominates the field. Pursuing and expanding on this tradition, I hold that emotions should be defined as dynamic episodes characterized by a high degree of coordination between several organismic subsystems in the interest of optimal adaptation to relevant events. The constitutive feature of emotions, ynchronization of response channels, is linked to the evolutionary origin of emotional expression by demonstrating that it is an essential aspect of spontaneous affect bursts in animals and humans. The significance of this mechanism to the signalling function in emotional expression communication is explored.