Patriarchal Chimpanzees, Matriarchal Bonobos: Potential Ecological Causes of a Pan Dichotomy

V. Sommer and C. Ross (eds.), Primates of Gashaka, Developments in Primatology: Progress and Prospects 35, DOI 10.1007/978-1-4419-7403-7_12, © Springer Science+Business Media, LLC 2011 Abstract Chimpanzees and bonobos, despite being closely related hominoid primates, differ in female gregariousness and dominance style. Violent male aggression is not atypical in chimpanzee societies and is vented against both other males and females in intraas well as inter-group conflicts; relationships amongst females are rather weak. Bonobo societies, on the other hand, are female-centred; reports about intergroup conflict are rare to absent but there are numerous reports of blood-drawing injuries inflicted upon males by coalitions of females. This dichotomy is of potential interest for the understanding of social dynamics in contemporary human societies, too, given that Pan and Homo shared a last common ancestor 5 – 6 million years ago. For example, political agendas to achieve a greater equality of the sexes might have to work against our natural inclinations, if the last common ancestor exhibited the patriarchal tendencies found in chimpanzees. Vice versa, if the last common ancestor possessed the matriarchal tendencies of bonobos, then patriarchal tendencies in contemporary human societies could be understood as rather recent cultural developments that can be more easily undone by counter-measures, i.e., changes in socio-economic dynamics. Such assertions are not unproblematic, given millions of years of evolution. Nevertheless, a reconstruction of the ancestral roots of the behavioural suites of Homo and Pan will have to rely on a causal understanding of the different species psychologies of chimpanzees versus bonobos. These should in some ways be related to ecology. Both species have a mixed diet dominated by fruit with a similar composition. To test if their diet differs in availability and quality, we collected data on habitat phenology and analysed nutritional content of food plants and non-food plants from a community of bonobos in Salonga National Park, Democratic Republic of Congo, and a community of chimpanzees living in Gashaka Gumti National Park / Nigeria.