Humans and Other Primates: Cultural Complexity in Mountain Gorillas and Bornean Orangutans

In our second year Humans and Other Primates  module, students are provided with a foundation in evolutionary anthropology through an understanding of primate biology and evolution. This week, we are featuring our second essay on this topic, by Hovnan Gulbenkian Eayrs.
Hovnan Gulbenkian Eayrs
Hovnan’s bio: I’m a second year student from Oxford. I discovered my interest in anthropology after studying human geography and biology at A-level. I think my mixed ethnic background and my love of people-watching have also contributed to my fascination with humans and our closest relatives.

Culture is not an easy thing to study and there are numerous definitions of the concept (Van Schaik et al., 2003). For some, culture is a way of describing how humans are unique and different from other animal species (Byrne, 2007). However, some definitions are more inclusive – one that is especially useful when comparing cultures is the idea that ‘culture’ refers to the social transmission of behaviours though a group of individuals (Van Schaik et al., 2003).

There are different reasons that scientists are interested in studying culture in non-human animals. One reason is that researchers want to find out how information is transmitted between animals and to understand what and how fast information moves around a group; another reason is due to the presumed status of culture as a trait that is only possessed by humans (Byrne 2007).

Studying the existence of culture in other animals is often done in a geographic way, in which researchers look at whether a behaviour is present or not in two or more different populations or groups within a species and between similar species (Robbins et al., 2016). There a number of ape species in which populations live in separate geographical locations with different ecologies (Doran & Mcneilage, 2002).

For example, Mountain gorillas (G. g. beringei) live in a different environment to their lowland relatives and so it is possible that traits in these individuals are cultural and come from social interactions (Byrne, 2007). There is not a large amount of evidence of cultural and social learning in gorilla species, even though they possess many traits that suggest strong possibilities that social learning is taking place (Robbins et al., 2016). This is similar in species of orangutan. The Bornean orangutan (Pongo pygmaeus) rarely show use of tools, however, they have high levels of cognitive ability (A. Delgado & Van Schaik, 2000). The evidence of tool use, gestural communication and technical food preparation that exists in both gorillas and orangutans are indications of their cultural complexity.

The use of tools in non-human primates is seen by many as an indication of the existence of culture (Laland & Hoppitt, 2003; Robbins et al., 2016). Tool use was defined by Van Lawick-Goodall in 1971 as “use of an external object as a functional extension of mouth or beak, hand or claw, in the attainment of an immediate goal” (Kinani & Zimmerman, 2015). Although tool use is very well documented in non-human primates in captivity – especially great apes – there is less evidence of it in the wild (Kinani & Zimmerman, 2015).

For example, in wild orangutans there is little evidence of tool use (Fox, et al., 2000), although they have been observed using different objects from their environment as tools for tasks such as collecting insects and hammering. This behaviour seems to be spontaneous and has only been observed in specific individuals (Fox, et al., 2000; Kinani & Zimmerman, 2015). In contrast, captive orangutans exhibit a wide array of uses for tools with quite complex tool-use behaviour, such as manufacturing tools for specific tasks or performing tasks with a large number of steps (Fox, et al., 2000). One explanation for this difference is that the mental capacity exists in wild orangutans but, due their solitarily lifestyle, there are fewer interactions between individuals, and so the use of tools, through observation and imitation, is less likely to take place (Van Schaik et al., 2003; Fox, et al., 2000). There is some evidence to support this explanation.  According to Fox et al. (2000), orangutans living in the Sauq Balimbing Research Area in Borneo were observed to spend more time in social groups then orangutans in other studies. As a result, they had more opportunity to pass along information and observe tool-use behaviour.  These individuals showed much more frequent and habitual tool use then had been observed before.

There is one use of tools that has been identified in wild Bornean orangutan that is not related to food gathering or preparation: the kiss-squeak, which is a type of auditory communication used by orangutans in distress. According to Hardus et al. (2009), some orangutans have been observed using leaves to cover their mouths whilst producing the kiss-squeak. This lowers the frequency of sound – as though it was produced by a much larger animal. The use of this tool in some individuals but not others, and its concentration in certain geographic locations, provides evidence that it is a cultural trait that is socially transmitted. Although this kind deceptive tool-use has never been reported in any other non-human animal, it challenges the idea that primate calls are controlled only by emotion, suggesting that it might be influenced by culture.

In contrast to the solitary behaviour of orangutans, mountain gorillas have strong cohesive social groups (Doran & Mcneilage, 2002; Kinani & Zimmerman, 2015). Because of this, it would be expected that due to a high level of social interaction, tool use culture would be frequently be passed between individuals. However, tool use in wild mountain gorillas has rarely been observed (Kinani & Zimmerman, 2015). According to Leca et al. (2010), whether innovations in use of tool become a cultural trait or tradition is largely to do with the environmental costs and benefits. Mountain gorillas live in an environment in which the main portion of their diet can easily be acquired without the use of tools; for this reason, there is very little evolutionary advantage for mountain gorillas to actively seek uses for tools (Kinani & Zimmerman, 2015).

In both mountain gorillas and orangutans, learning can take place vertically, from a mother to her child (Fox, et al., 2000; Kinani & Zimmerman, 2015; Van Schaik et al., 2003). Fox et al. (2000) report that infant orangutans were frequently observed watching intently while tools were being used. In these situations, the infant was often observed playing with the tool or sometimes repeating the behaviour after the mother had discarded the tool, which shows a level of ability to comprehend an action performed and then imitate it. These tool-use behaviours have been shown to become habitual in the infants after they become independent (Fox, et al., 2000). There is even some evidence that these same behaviours are adapted and changed to suit the needs of the tool user (Van Schaik et al., 2003). In mountain gorillas, similar behaviour has been observed, although there is little evidence of tool-use being passed between individuals (Kinani & Zimmerman, 2015).

Another behaviour in great apes useful for identifying culture and its complexity is feeding skills (Byrne, 2007). Most orangutan populations cannot create elaborate tools; however, they do show complex food preparation skills, especially when consuming plants with spines or thorns. Similarly, complex plant processing without the use of any tools is a trait that has been frequently observed in gorillas (Byrne, 2007). This processing often involves many different steps and goes far beyond processes observed in other great apes such as chimpanzees (Byrne, 2007).

In mountain gorillas, several kinds of social interactions have been identified as possible cultural traits. According to Robbins et al. (2016), these behaviours include: placing arms on the back of the gorilla in front while moving, feeding for show and playing chase around a tree, and are not observed in other populations of gorillas. Equally, some social behaviour and gestures have only been observed in other gorilla populations, supporting the idea that these behaviours are due to cultural transmission. For example, hand clapping is a gesture that has been observed in all species of gorilla apart from mountain gorillas, which strongly suggests that it geographically specific and may be culturally learned (Robbins et al. 2016).

As wild orangutans have few social interactions, it would be expected that they have fewer gestures and social behaviours; however, over 64 gestures have been identified in captive orangutans, including twenty-nine that were used very frequently (Cartmill & Byrne, 2010). In wild and captive orangutans, some single gestures have been identified to have specific meanings (Cartmill & Byrne, 2010). Similarly, in Pika et al.’s (2005) study of young gorillas, they identified some gestures that seemed to be learned from a young age that had very specific meanings in certain contexts.

Although the method of ‘exclusion’ or ‘geographical comparison’ is a good way of obtaining evidence of cultural complexity, it does not take into account the influence of ecology and genetics in the differences in behaviour between groups (Langergraber et al., 2010; Robbins et al., 2016; Byrne, 2007). There is a possibility that the ‘cultural’ traits that have been observed in both orangutans and gorillas are simply caused by the fact that the individuals observed live in a very similar environment. In this case the evidence of these behaviours and traits are not really any evidence for culture or cultural complexity in either species (Langergraber et al., 2010).This brings us back to the question of how culture should be defined and whether it is only transferred socially. Although there continues to be much debate in the scientific community on this matter, answering this question is fundamental in understanding the origins of our species (D’Errico, 2003).

References

Delgado, R. & Van Schaik, C. P., 2000. The Behavioral Ecology and Conservation of the Orangutan (Pongo pygmaeus): A Tale of Two Islands. Evolutionary Anthropology.

Byrne, R. W., 1999. The Mentalities of Gorillas and Orangutans: Comparative Perspective. Cambridge: Cambridge University Press .

Byrne, R. W., 2007. Culture in great apes: using intricate complexity in feeding skills to trace the evolutionary origin of human technical prowess. The Royal Society, Volume 362, p. 577–585.

Cartmill, E. & Byrne, R., 2010. Semantics of primate gestures: intentional meanings of orangutan gestures. Animal Cognition, 13(6), p. 793–804.

D’Errico, F., 2003. The invisible frontier. A multiple species model for the origin of behavioral modernity. Evolutionary Anthropology, Volume 12.

Doran, D. M. & Mcneilage, A., 2002. Gorilla Ecology and Behavior. Evolutionary Anthropology.

Fox, E., Sitompul, A. & Van Schaik, C., 2000. Intelligent tool use in wild Sumatran orangutans. In: The Mentalities of Gorillas and Orangutans : Comparative Perspectives. Cambridge: Cambridge University Press, pp. 200-216.

Hardus, M. E., Lameira, A. R., Van Schaik, C. P. & Wich, S. A., 2009. Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?. The Royal Society, Volume 10.

Kinani, J.-F. & Zimmerman, D., 2015. Tool Use for Food Acquisition in a Wild Mountain Gorilla (Gorilla beringei beringei). American Journal of Primatology, Volume 77, p. 353–357.

Laland, K. & Hoppitt, W., 2003. Do Animals Have Culture. Evolutionary Anthropology, Volume 12, pp. 180-189.

Langergraber et al., K. E., 2010. Genetic and ‘cultural’ similarity in wild chimpanzees. The Royal Society, Volume 278.

Pika, S., Liebal, K. & Tomasello, M., 2005. Gestural Communication in Young Gorillas (Gorilla gorilla):Gestural Repertoire, Learning, and Use. American Journal of Primatology , Volume 60.

Robbins et al., M. M., 2016. Behavioral Variation in Gorillas: Evidence of Potential Cultural Traits. PLoS ONE, 11(9).

Van Schaik et al., C. P., 2003. Orangutan Cultures and the Evolution of Material Culture. Science, Volume 299.

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