• Questioning the “sexy” bonobo hype, part 2: a primatologist debunks Christopher Ryan

    Read part 1 to get up to speed. See also follow-up post for even more.

    Following the first post on the subject, Christopher Ryan left comments to say that the primatologist colleague I had cited was incorrect about how extensively bonobos have been studied. He also made some unnecessary personal attacks, while saying little about the substance of that post.

    QuoteBetween then and now, two more primatologists have contacted me about bonobos. Them, and all of the primatologists I have ever spoken to on this subject, believe that Ryan’s take is misleading and erroneous. One has given me permission to post their rebuttal. It is printed below, unedited. I will honor their wish for anonymity, a wish that makes a good deal of sense if you read the comments of my last post and witness just how quickly personal insults get resorted to in this business of public skeptical discourse.

    ok, couple of major points. 1- The New Yorker’s Ian Parker has noted that “It is one of the oddities of the bonobo world—and a source of frustration to some—that Frans de Waal… has never seen a wild bonobo.” I have, a lot. Before I began studying this species I naturally read up on most of de Waal’s work. Some captive animal species can provide viable data for interpretation, i.e. how they behave in captivity can be assumed is how they behave in the wild. Bonobos are most certainly not one of these species. There are many reasons for this but lets stick with the basics.

    1 – In captivity their social grouping is totally artificial and not in line with how these animals group and disperse in the wild

    2 – If you put a group of male and female humans in a cage with nothing to do and provide them shelter and food, what do you think they would do all day – have sex!

    Natural bonobo behaviour and society is neither female dominated nor sex crazy. Data sets from the wild clearly show that over the course of a year female bonobos do not copulate any more than female chimpanzees. So let’s put that myth to bed right now. Females are not dominant over males in the sense that all male chimpanzees are dominant over all female chimpanzees. This is a very poorly understood area and we predict that future results will show that their dominance system is more to do with mother/son coalitions.

    Bonobos are violent. Granted they are not as violent as chimps but then what animal is? They fight and aggress each other just like any other group living species that have intragroup competition. Males sometimes rip infants from their mothers arms and bully the mothers. It happens, it’s a reality and an adaptive function of normal bonobo society.

    Copulating face to face – again, guess where this idea came from – captivity. Where they don’t have trees to climb in. I’ve recorded hundreds of copulations in wild bonobos. Want to know what percentage was ventral-ventral? 5%. All ventral-ventral copulations were when they were on the ground. It’s not about being face to face, it’s about what position is most convenient.

    Bonobos – not sex crazed, not peace loving, not female dominated. But easily the most intriguing and wonderful species to ever see and study in the wild. We don’t need to cling on to this anti-chimp image we are so desperate to give them. Their real behaviour is far more interesting.

    Several published papers substantiate some details given above. Note, these are all observations of bonobo behavior in the wild, not in captivity. Surbeck et al. (2011) described the existence of male-male dominance hierarchy, the strong correlation between this aggression-based dominance hierarchy and reproductive success, and the importance of mother/son kin support in male-male dominance contests contra ideas of “females run things”. Additionally, I found it relevant that they recorded 134 aggressive interactions when “conflicts arose over access to oestrous females”.

    Surbeck & Hohmann (2013) reported in their analysis of intersexual dominance across contexts that the LuiKotale bonobos have a mixed-sex hierarchy, not a females- or males-rule. They also observed the frequency with which females win a conflict (vs a male) depended on which context (food competition, mating, social challenge); for example females won 58% of the time in the feeding context but only 44% in the mating context. Females lost many conflicts because some females were subordinate to some males.

    Mixed-sex (or rather, sex-independent dominance) hierarchy is also reported by Furuichi (1997), Paoli et al. (2006), and Hohmann et al (1999). Wood and White (2007) went so far as to say males dominate but are sometimes deferent about food, writing,  “Males were consistently dominant in dyadic interactions.”

    I am no primatologist, but I could find no field research consistent with Ryan’s claims, nor do any of the half-dozen primatologists I have talked to agree with most of his claims about bonobos.

    EDIT (1/19/15) The first paragraph of the quoted material has been edited to include new information.

    Suggested reading
    Swingers” by Ian Parker in The New Yorker (2007) quotes Hohmann, Craig Stanford, Jeroen Stevens and others substantiating the claims above.

    Sex at Dusk by Lynn Saxon. A thorough rebuttal to Christopher Ryan’s Sex at Dawn.


    T. Furuichi (1997). Agonistic interactions and matrifocal dominance rank of wild bonobos (Pan paniscus) at Wamba, Zaire. Int J Primatol 18:855–875.

    G. Hohmann, U. Gerloff, D. Tautz and B. Fruth (1999). Social Bonds and Genetic Ties: Kinship, Association and Affiliation in a Community of Bonobos (Pan paniscus). Behavior. Vol. 136, No. 9, Genetic Analysis of Social Systems (Oct., 1999), pp. 1219-1235

    Martin Surbeck, Roger Mundry, Gottfried Hohmann (2011). Mothers matter! Maternal support, dominance status and mating success in male bonobos (Pan paniscus). Proc. R. Soc. B:2011278 590-598;DOI: 10.1098/rspb.2010.1572.

    Martin Surbeck, Gottfried Hohmann (2013). Intersexual dominance relationships and the influence of leverage on the outcome of conflicts in wild bonobos (Pan paniscus). Behav Ecol Sociobiol. 67:1767–1780

    Paoli T, Palagi E, Tarli SMB (2006). Reevaluation of dominance hierarchy in bonobos (Pan paniscus). Am J Phys Anthropol 130:116–122.

    White, F. J. and Wood, K. D. (2007), Female feeding priority in bonobos, Pan paniscus, and the question of female dominance. Am. J. Primatol., 69: 837–850. doi: 10.1002/ajp.20387

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  • Article by: Edward Clint

    Ed Clint is an evolutionary psychologist, co-founder of Skeptic Ink, and USAF veteran.