Sexy Bonobos

Bonobos kissing while grooming

To study the role of sex in behavior and evolution this week, we used the bonobo, our genetically closest living ancestor. We read the article “The Other ‘Closest Living Relative’: How Bonobos (Pan paniscus) Challenge Traditional Assumptions about Females, Dominance, Intra- and Intersexual Interactions, and Hominid Evolution,” (2000) which outlines the sexual and reproductive behaviors of bonobos and suggested theories to explain these behaviors. According to the research, female bonobos are very much in control of their own reproductive and social interactions, having been observed attacking males who refuse to mate with them, high-ranking males protesting a female copulating with a low-ranking male, and low-ranking males they are mating with when a high-ranking male threatens. There is some debate as to what female behavior we call “dominant” or “co-dominant,” and there appears to some bias in distinguishing between male and female behavior.

They explain a few different viewpoints and hypotheses to explain this behavior and different interpretations of it. The first is the “Traditional View,” in which they suggest that patterns of dispersal are predictive of patterns of bonding. Chimpanzees have much stronger male-male relationships, believed to based off of evolutionary fitness, and females are also the dispersing sex, avoiding one another and the aggression of males. In bonobos, females are the dispersing sex, there is less male-male sociality than in chimpanzees (despite inter-relatedness), and males and females groom each other continuously (regardless of reproductive state). The “Revised View” holds that the relationships between dispersal pattern, bonding, and relatedness may not follow theoretical predictions. Some female chimpanzees have a reproductive strategy in which their infants are sired by males from other communities, which is desirable because they often don’t disperse as much as previously believed. This also means male-male relationships are not based on relatedness or fitness. They use extra-group paternity as an example against the theory of the bonding-philopatry relationship. Bonds between males and females are actually weaker than previously believed (besides mother-son bonds). The strongest unrelated relationships are between females, and grooming reflects social ranking within these female-female relationships. Studying female-female relationships, according to the authors, are key to understanding bonobo social organization.

Something interesting they mention early on in the article is the variability in behavior within the species of chimpanzees and bonobos (by population). A major take-away from this week is that, although it creates less cognitive dissonance for us to be able to neatly classify entire species (also meaning all of the populations and sub-species within a species) into different group social structures, it is not always accurate or pragmatic to do so. It is exclusive, all-or-none classifications like these that led to the biases in interpreting observed behavior that we have today. They prevent primatologists from approaching observation with a more open mind, as a major bias in research is the self-confirming bias. Rather than “species-typical” characteristics, most primatologists now believe that behavioral differences between chimpanzees and bonobos can be attributed to both ecological opportunities and constraints, leading to diverse selection pressures. Although somewhat in opposition to this theory, it is also worth mentioning that a study done on chimpanzees and bonobos living in identical captive environments still exhibited distinct behavioral characteristics. Bonobos engaged in co-fishing and sex when fishing for termites, while chimpanzees did not eat together and did not engage in sex while fishing for termites. Something even more interesting is that bonobo behavior observed in this specific captive environment reflected behavior in other captive environments and data collected from wild bonobos in the field.

I think that studying bonobo sexual behavior can tell us a lot about our own sexual behavior. Having taken the psychology course Human Sexuality, I know that studying human reproduction and sexual behavior has always been something both fascinating and important to us. The Parish and De Waal (2000) article emphasizes the need to expand our own models for human evolution based off of bonobo research to include some of the unique relationships that they share. I believe that by studying bonobo sexuality and by comparing and contrasting their behaviors to those of our own, we can take a step into the evolutionary past and perhaps track where certain behaviors developed and what factors (social, cultural, ecological, etc…) pushed for some behaviors to make us more adaptive. Perhaps we can even make speculations about the sexual behavior of Australopithecines and early Homo species from which we evolved and which link us to the bonobo.

SOURCES

Parish, A.R. and De Waal, F.B.M. (2000), The Other “Closest Living Relative”: How Bonobos (Pan paniscus) Challenge Traditional Assumptions about Females, Dominance, Intra- and Intersexual Interactions, and Hominid Evolution. Annals of the New York Academy of Sciences, 907: 97–113.

Strier, K.B. (2011) Primate Behavioral Ecology, 4th Edition, Pearson/Prentice-Hall.

https://stewmm0.files.wordpress.com/2014/02/98fe8-2707603567_ca40bdabe0_o.jpg (PHOTO)