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Gonzaga Professor Bodamer, Colleagues Publish Findings that Chimpanzees Create Social Traditions

Two chimpanzees engage in a palm-to-palm grooming handclasp. © Gonzaga University Professor Mark Bodamer
Two chimpanzees engage in a palm-to-palm grooming handclasp. © Gonzaga University Professor Mark Bodamer

‘A Clear-Cut Example of Cultural Traditions’

SPOKANE, Wash. – Research published Aug. 29 by Gonzaga University psychology Professor Mark Bodamer and four collaborating international scientists has revealed that chimpanzees are not only capable of learning from one another, but also use this social information to form and maintain local traditions.

The research shows that the ways chimpanzees groom each other depends on the community to which they belong. Specifically, it is the unique handclasp grooming behavior that reveals this local difference. The study, titled “Neighbouring Chimpanzee Communities Show Different Preferences in Social Grooming Behaviour” is reported in the journal Proceedings of the Royal Society B. Read the complete journal article.

“It’s a clear-cut example of cultural traditions,” Bodamer said. “What we found is variation in that behavior in terms of the actual hand-clasping. These chimpanzees handclasp quite often and, thanks to the efforts of many, we have a very large data set of photos, video and field notes. Many examples were recorded by Gonzaga undergraduate students who took part in this study. The students also collected other behavioral observation data as part of the Gonzaga in Chimfunshi summer program.”

Bodamer’s co-researchers include Katherine A. Cronin, Edwin J.C. van Leeuwen, and Daniel B.M. Haun from the Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands; and Roger Mundry, from the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.

The research took place at the 24,000-acre Chimfunshi Wildlife Orphanage Trust in Zambia through the Gonzaga in Chimfunshi program, and is part of Gonzaga’s Study in Zambia initiative, which includes the Gonzaga in Zambezi Intercultural Servant Leadership Program and the Gonzaga in Monze Teacher Education program. In Zambia, Gonzaga students explore academically and socially relevant topics, in context, and take direct action to address economic, environmental and educational challenges.


Handclasp Grooming

The specific behavior the researchers focused on was the “grooming handclasp,” in which two chimpanzees clasp onto each other’s arms, raise those arms up in the air, and groom each other with their free arm (see photo above). While this behavior has been documented before, the question remained regarding whether chimpanzees are instinctively inclined to engage in grooming handclasp behavior or if they learned this behavior from each other and pass it on to subsequent generations.

VIDEO: Click the video below to see chimpanzees “Daisey” and her mother “Diana” engaging in a palm-to-palm grooming handclasp; then, they switch to the wrist-to-wrist style. The video was filmed by researcher Patrick Mwika at Chimfunshi Wildlife Orphanage.

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Cultural Significance

Previous research suggested the grooming handclasp might be a cultural phenomenon, just as humans across cultures engage in various greeting behaviors. However, these suggestions were primarily based on observations that some chimpanzee communities handclasp and others don’t – not whether there are differences between communities that engage in the handclasp behavior. Further, the early observation that only some groups engage in the handclasp behavior could be explained by differences in genetic or ecological factors (or both) between the chimpanzee communities, which precluded the interpretation that the chimpanzees were exhibiting “cultural” differences.

Different Styles of Handclasping

(Left) An example of palm-to-palm grooming handclasp. (Right)wrist-to-wrist grooming handclasp. © Gonzaga University Professor Mark Bodamer

This new study contributes significantly to research by showing that subtle-yet-stable differences exist between chimpanzee communities that engage in the grooming handclasp with respect to the styles of grooming they prefer. For example, one chimpanzee group much preferred the style in which they would grasp each other’s hands during grooming; another group engaged more in a style characterized by the folding of their wrists around each other’s wrists (see photos above).

“We don’t know what mechanisms account for these differences,” van Leeuwen said. “But we do know that these chimpanzee communities formed and maintained their own local grooming traditions over the last five years. In conjunction with observations in other species, it appears that humans are not the only species with social traditions. Our observations may also indicate that chimpanzees can overcome their innate predispositions, potentially allowing them to manipulate their environment based on social constructs rather than on mere instincts.”

The research team also observed that the grooming handclasp behavior was a long-lasting part of the chimpanzees’ behavioral repertoire: the behavior was even transmitted to the next generation.

Young Chimps Learn Local Traditions

“By following the chimpanzees over time, we were able to show that 20 young chimpanzees gradually developed the handclasp behavior over the course of the five-year study,” Bodamer said. “The first handclasps by young individuals were in partnership with their mothers. These observations support the conclusion that these chimpanzees socially learn their local tradition, and that this might be evidence of social culture.”

Read the full news release online.

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