| Gestures are integral components of human and non-human primate communication. In humans, children rely extensively on gesturing before speech develops (Knott 1979) and gestures remain important to communication even after the development of speech (Dunning 1971; Melinger & Levelt 2004). Gestural signaling is also central to communication in other primates, particularly African apes (Pika et al. 2005a). Neurological research reveals structural similarities between key language networks in the brain and manual actions in humans and nonhuman primates, providing evidence for an evolutionary continuity between language and bodily actions among primates (Kelly et al. 2002; Arbib 2005). Although much has been learned about gestural signaling in primates, an understanding of how and why gestural repertoires vary across species and what role gestures played in language evolution is incomplete.;This dissertation investigated how two factors, social dynamics (the nature of social relationships) and positional behavior (locomotor and postural behavior), shaped gestural communication within and across captive groups of western lowland gorillas (Gorilla gorilla gorilla), chimpanzees (Pan troglodytes sspp.), and bonobos (Pan paniscus ). I conducted this research with six captive groups over the course of twenty-four months. Subjects included: (1) Two groups of western lowland gorillas at the Bronx Zoo, NY; (2) Two groups of chimpanzees at the St. Louis Zoo, MO, and Los Angeles Zoo, CA; and (3) Two groups of bonobos at the San Diego Zoo and San Diego Wild Animal Park, CA. I used a Sony Handycam to collect continuous video data of social interactions (from which I coded various aspects of gestural signaling) and 15- minute focal animal sampling (from which I coded frequencies and durations of positional behaviors).;While there was some level of inter-group variation in all species, patterns of gestural communication were accurate measures of the unique social dynamics that characterize each species. Gesturing was not restricted by the availability of the upper limbs; rather, positional behavior was often used to enhance certain gestures, particularly dominance displays. These results demonstrate that gestural signaling expresses the kind of behavioral and locomotor plasticity that could have given rise to a flexible, complex form of communication that eventually became language. |
