The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


The relationship between gestural signaling and positional behavior in chimpanzees and bonobos

LINDSEY W. SMITH.

Thompson Writing Program, Duke University

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The gestural repertoires of chimpanzees and bonobos are well documented, but the relationship between gestural signaling and positional behavior (postures and locomotion) is unresolved. This study examines how gestures and positional behavior shape each other and how this relationship varies across two closely related species in similar environments. From September 2007 to June 2008, 500 hours of video data were collected from four groups: chimpanzees at the St. Louis Zoo and Los Angeles Zoo, and bonobos from the San Diego Zoo and San Diego Wild Animal Park. 2,041 chimpanzee gestures and 3,486 bonobo gestures were recorded and coded in terms of the positional behaviors of the actors.

Chimpanzees gestured most frequently while sitting (35.5% of total gestures), while bonobos gestured most frequently while lying (24.0% of total gestures). Both species also gestured frequently while bipedal (10.7% of chimpanzee and 11.2% of bonobo gestures), though 95.3% of these gestures were produced by infant bonobos. Adult chimpanzees gestured more while bipedal than adult bonobos, but these gestures were rarely manual gestures involving the upper limbs. Rather, positional behaviors were often incorporated into the communicative acts. For example, among adult male chimpanzees, the gesture “bipedal swagger” (involving piloerection and exaggerated swaying) accounted for 74.3% of the gestures produced while bipedal walking. These results reveal a complex interplay between gestures and positional behavior, but provide little evidence that bipedality facilitates manual gesturing. Understanding this relationship is crucial for testing theories about human language origins, particularly whether bipedality prompted increased manual gesturing in early hominins.

This research was funded by the American Association of University Women (American Dissertation Fellowship), CUNY Mario Capelloni Dissertation Fellowship, Sigma Xi Grant-in-Aid of Research, CUNY Graduate Center Research Grant for Doctoral Studies, and the New York Consortium for Evolutionary Anthropology.

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