Gestural Iconicity and Alignment as Steps in the Evolution of Language.

Studies of the evolution of language rely heavily on comparisons to nonhuman primates, particularly the gestural communication of nonhuman apes. Differences between human and ape gestures are largely ones of degree rather than kind. For example, while human gestures are more flexible, ape gestures are not inflexible. In this piece, I closely consider two features of the gestural communication of apes and humans that might display differences in kind: iconicity and temporal alignment. Iconicity has long played a privileged role in theories of gestural language origins, the proposal being that it provided a steppingstone into language through a stage of pantomime. However, iconicity is not as easy as it seems. Evidence from co-speech gestures of hearing children and from homesign suggests that iconic reference is both cognitively complex and slow to develop in humans. There is no conclusive evidence that nonhuman apes understand or produce iconic gestures; some gestures may appear iconic to human observers but the apes themselves may not understand the similarity between form and meaning. Far from providing an easy pathway into the emergence of symbolic communication, iconicity relies on sophisticated capacities for analogy and abstraction, ones often lacking in apes and young children. Temporal alignment between gesture and vocalization is another area that may show sharp contrasts between adult humans and apes, though data here is sparser. I discuss the tight synchronization of gesture and speech that emerges over the first year of life in human children and contrast it with gesture and vocalization in apes, which typically are described as overlapping but not simultaneous. Human ancestors probably communicated in ways similar to other apes, but the dual emergence of the ability to use iconic reference and the alignment of hand and mouth may have set our ancestors down a unique evolutionary road toward language.