TY - JOUR
T1 - Characterization of Pan social systems reveals in-group/out-group distinction and out-group tolerance in bonobos
AU - Samuni, Liran
AU - Langergraber, Kevin E.
AU - Surbeck, Martin H.
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank the Institut Congolais pour la Conservations de la Nature and the Ministry of Scientific Research and Technology in the Democratic Republic of the Congo for their support and permission to work in the Kokolopori Bonobo Reserve, Democratic Republic of Congo; the Uganda Wildlife Authority, and the Uganda National Council for Science and Technology for permission to work in the Kibale National Park; Sam Angedakin, Sebastian Ramirez Amaya, and Kevin Lee for assistance with the long-term database at Ngogo; John Mitani and David Watts for logistical support; the Bonobo Conservation Initiative and Vie Sauvage, especially Sally Coxe and Albert Lotana Lokasola, for supporting our work; the Kokolopori Bonobo Research Project and Ngogo Chimpanzee Project staff members; and Alexander Mielke and Erin Wessling for helpful discussions and comments. Funding was provided by Harvard University, Arizona State University, and the Max Planck Society.
Publisher Copyright:
Copyright © 2022 the Author(s).
PY - 2022/6/28
Y1 - 2022/6/28
N2 - Human between-group interactions are highly variable, ranging from violent to tolerant and affiliative. Tolerance between groups is linked to our unique capacity for large-scale cooperation and cumulative culture, but its evolutionary origins are understudied. In chimpanzees, one of our closest living relatives, predominantly hostile between-group interactions impede cooperation and information flow across groups. In contrast, in our other closest living relative, the bonobo, tolerant between-group associations are observed. However, as these associations can be frequent and prolonged and involve social interactions that mirror those within groups, it is unclear whether these bonobos really do belong to separate groups. Alternatively, the bonobo grouping patterns may be homologous to observations from the large Ngogo chimpanzee community, where individuals form within-group neighborhoods despite sharing the same membership in the larger group. To characterize bonobo grouping patterns, we compare the social structure of the Kokolopori bonobos with the chimpanzee group of Ngogo. Using cluster analysis, we find temporally stable clusters only in bonobos. Despite the large spatial overlap and frequent interactions between the bonobo clusters, we identified significant association preference within but not between clusters and a unique space use of each cluster. Although bonobo associations are flexible (i.e., fission-fusion dynamics), cluster membership predicted the bonobo fission compositions and the spatial cohesion of individuals during encounters. These findings suggest the presence of a social system that combines clear in-group/out-group distinction and out-group tolerance in bonobos, offering a unique referential model for the evolution of tolerant between-group interactions in humans.
AB - Human between-group interactions are highly variable, ranging from violent to tolerant and affiliative. Tolerance between groups is linked to our unique capacity for large-scale cooperation and cumulative culture, but its evolutionary origins are understudied. In chimpanzees, one of our closest living relatives, predominantly hostile between-group interactions impede cooperation and information flow across groups. In contrast, in our other closest living relative, the bonobo, tolerant between-group associations are observed. However, as these associations can be frequent and prolonged and involve social interactions that mirror those within groups, it is unclear whether these bonobos really do belong to separate groups. Alternatively, the bonobo grouping patterns may be homologous to observations from the large Ngogo chimpanzee community, where individuals form within-group neighborhoods despite sharing the same membership in the larger group. To characterize bonobo grouping patterns, we compare the social structure of the Kokolopori bonobos with the chimpanzee group of Ngogo. Using cluster analysis, we find temporally stable clusters only in bonobos. Despite the large spatial overlap and frequent interactions between the bonobo clusters, we identified significant association preference within but not between clusters and a unique space use of each cluster. Although bonobo associations are flexible (i.e., fission-fusion dynamics), cluster membership predicted the bonobo fission compositions and the spatial cohesion of individuals during encounters. These findings suggest the presence of a social system that combines clear in-group/out-group distinction and out-group tolerance in bonobos, offering a unique referential model for the evolution of tolerant between-group interactions in humans.
KW - bonobo
KW - chimpanzee
KW - grouping patterns
KW - intergroup relations
KW - social structure
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U2 - 10.1073/pnas.2201122119
DO - 10.1073/pnas.2201122119
M3 - Article
C2 - 35727986
AN - SCOPUS:85132247806
SN - 0027-8424
VL - 119
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 26
M1 - e2201122119
ER -