Humans and other primates: the differences in cultural complexity between orangutans and chimpanzees

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, our featured essay is by Daniel Wright.
Daniel Wright
Daniel’s bio: I am a second year anthropology student from South East London. Since a very young age, I have been keen on gaining a deeper understanding of the complexity of humans, and their place in nature relative to other species.

Culture can be defined as “Information capable of affecting individuals’ behaviour that they acquire from other members of their species through teaching, imitation, and other forms of social transmission” (Richerson and Boyd, 2005).It is important to note, however, that many anthropologists have distinct ideas of what they mean by culture, and this is partly due to what they intend to investigate in their studies. In the past, culture has been thought to be a trait unique to humans (Whiten et al, 1999), but it is becoming apparent that many other species of primates, particularly in other ape species such as orangutans (pongo pygmaeus)and chimpanzees (Pan troglodytes), also exhibit culture. There are various social and environmental factors which affect the ways in which culture is transmitted to other individuals in a population, and this makes culture in these species quite complex, particularly between different populations. In light of this, many studies have been conducted which provide us with an understanding of how cultural variation occurs between these species. These studies will be the focus of the essay and will be discussed from a critical point of view, in terms of what these studies tell us, and that both social and environmental factors influence cultural variation in these species.

The social transmission of culture from one individual to another in a population of a species usually occurs through social learning, both direct (through imitation, copying actions themselves) and indirect (through local enhancement, making a connection between a stimulus, and its result) (Castro and Toro, 2004). This is demonstrated in a study conducted by Call et al (2005), which looked at whether chimpanzees could copy the actions of others, using methods which exist outside of their usual behavioural strategies. The study consisted of chimpanzees and human children, in which both were shown different methods of opening a tube, but in different experimental conditions. It was discovered from this study that chimpanzees emulate behaviour through seeing the result, whereas the children imitated the actions themselves (Call et al, 2005). This tells us that chimpanzees use their environment to achieve a desired result i.e. through responding to a stimulus, which also supports the idea of culture as something that is acquired through learning. This would suggest that environmental influences have a greater impact on the manifestation of cultural traits within chimpanzees, than social influences.

An earlier study conducted by Whiten et al (1996), however, found that chimpanzees did imitate the demonstrator’s actions in a problem-solving task. In this study, the demonstrators performed somewhat complex actions for chimpanzees to imitate, as well as irrelevant ones, which included attempting to open a box. In one of these conditions, the demonstrator twisted the bolt to open the box, which was not necessary in order to get the box open. It was later observed that some of the chimpanzees had also performed this action, even though there was no advantage in doing so, which Whiten had interpreted as evidence to suggest they had imitated the behaviour (Whiten et al, 1996). This potentially tells us about foraging behaviours in chimpanzees and would suggest a greater emphasis on social influences of behaviours in chimpanzees, implying that cultural differences between species are more social in nature than environmental.

Tomasello (1996), however, pointed out that just because this behaviour was observed in the chimpanzees, does not necessarily mean it was a result of social learning; it may have been perceived merely as a desirable outcome for the chimpanzees. This highlights a greater issue in attempting to study culture in other primates in nature, pointed out by Van Schaik in his study on the relationship between geographic variation and cultural variation in orangutans: it is difficult to ascertain whether observed behaviours are socially transmitted, and therefore whether they can be considered a cultural trait (Van Schaik et al, 2003).

Within this study, Van Schaik et al (2003) attempts to establish whether geographic distance in the behaviour of orangutans can explain whether culture exists in other ape species, and if so, the cultural variants that exist between populations, which may also shed light on whether geographic distance can explain cultural differences between species. They identify different variants within orangutans and classify them in terms of their likelihood of being socially transmitted behaviours, then observe which variants are customary, habitual, rare, absent, or unknown from six different study sites between Sumatra and Borneo. They also examine the relationship between these observations and their geographical distance from one another. The researchers conclude that there is a correlation between geographic distance and cultural differences, as well as a correlation between opportunity for social learning to occur and the size of the cultural repertoire (Van Schaik et al, 2003). They also find that there is no effect of habit on the content of culture. From this study, we can infer that orangutans are less imitative than chimpanzees, but there is still a strong correlation between social and learning and the cultural traits they exhibit in their behaviours. This would suggest that social influences have a greater impact on cultural variation than environment does, given that habitat had no effect on the cultural traits of the orangutans.

On the other hand though, various critics have suggested that the geographic approach can create errors in judgement, as it may lead the researcher to conclude that cultures exist, when it could actually be due to ecological differences (unrecognized by the researcher) between sites producing convergence within populations, and divergence between populations, through individual learning (Galef, 1992; Tomasello, 1999). Because culture is socially transmitted from one individual to another through social learning and observation, this would not constitute culture. If that is the case, then this suggests that the environment could potentially play a bigger role in the cultural variation between species than social influences and highlights the limitations of the researcher in these studies, and where there may be a case for further study.

Another study on orangutans conducted by Call et al (1995) looked at problem solving skills and social learning in juvenile and adult orangutans and, again, with human children. Within this study, the orangutans were made to operate a simple apparatus with a reward inside, but were unaware of an internal mechanism, to avoid individual learning within the experiment. This study was repeated multiple times in different experimental conditions, in which they had observed a human demonstrator, orangutan demonstrators, orangutans that had been shown human actions, and they found that in all these experiments, the orangutans did not show any imitative behaviour. Despite this though, they did show emulative behaviour, in which they attempted to solve the problem on their own, using trial and error. Again, this suggests that chimpanzees may have a more diverse process of social transmission than orangutans, and also that orangutans are more solitary than chimpanzees, as they tend to learn individually.

Given that in other studies orangutans have been observed performing human-like behaviours (Russon and Galdikas, 1993), it is not the case that orangutans are unable to perform these actions, it is more the case that they are not able to imitatively learn instrumental actions by observing the behaviours of others (Call et al, 1995). The findings of this study support the idea that orangutans have emulative behaviour, and are skilful at problem solving with the use of tools (Galdikas 1982; Lethmate 1982), but are not imitative of others’ behaviour. This differs from chimpanzees, as there have been more reports of imitative behaviour in chimpanzees than in orangutans. This also suggests that there is an environmental impact on orangutans, but they tend to be individual learners, and so perhaps they have less culture than chimpanzees.

Conversely, in a study conducted by Russon and Galdikas (1993), they had observed spontaneous imitative behaviours in orangutans that were excaptives. In this study, they used subjects living in ‘enriched’ environments, in rehabilitation, and collected a sample of spontaneous imitations and analysed the most complex ones to verify whether these were indeed instances of true imitation. This consisted of 395 hours of observation of 26 orangutans, in which they identified 354 incidences of imitation. 54 of these incidences were complex but difficult to explain by forms of imitation that were based on processes that were associative and grounded in experiential learning (Russon and Galdikas, 1993). It was concluded that orangutans, and possibly other great ape species, may have imitative behaviour. It was also pointed out that environmental factors were critical to imitative performance. This supports the notion that environmental factors do have an impact on cultural traits, but also shows that imitative behaviours can be exhibited by orangutans, given the right circumstances.

The idea of great ape species exhibiting imitative behaviour in certain circumstances can also be found in chimpanzees. In a study conducted by Whiten et al (2001), chimpanzee communities were studied long-term at nine different sites and were chartered through a systematic and collaborative procedure where 65 behaviour patterns were confirmed to be observed, and the frequencies of these behaviours were observed in each of these communities. More than half of these behaviours were seen to be cultural variants and were frequent enough at one or more sites to be considered a result of social transmission, but absent where environmental explanations were rejected. It was observed that each community had unique cultural traits, which exceeded any reports of cultural variation in non-human primates prior to this study (Whiten et al, 2001). This study suggests that chimpanzees have a much higher rate of cultural variation than orangutans and are a much more sociable species. The fact that cultural variants were not seen at sites where environmental explanations were rejected shows the importance of environmental factors in shaping culture within a population or species; this has been shown to be the case in a more diverse sense with chimpanzees than with orangutans.

Based on these studies, it appears to be the case that there is a clear difference in cultural variation between chimpanzees and orangutans, and that these cultural differences are largely based on both social factors and environmental factors. However, the social factors seem to have a greater impact on chimpanzees, where as environmental factors have a greater impact on orangutans. This could be because orangutans tend to live quite solitary lifestyles compared to chimpanzees, and so they learn more individually, rather than through imitation, which is more common in chimpanzees. It is important to note however, that it is difficult for the anthropologist to have accurate depictions of what can be considered cultural traits, and whether these are socially transmitted or not (Van Schaik et al, 2003).


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