This paper explores the role of iconicity in spoken language and other human communication systems. First, it concentrates on graphical and gestural communication and shows how semantically motivated iconic signs play an important role in creating such communication systems from scratch. It then considers how iconic signs tend to become simplified and symbolic as the communication system matures and argues that this process is driven by repeated interactive use of the signs. It furthermore looks at evidence for iconicity at the level of the system in graphical communication and finally draws comparisons between iconicity in graphical and gestural communication systems and in spoken language.