One of the top 125 questions of our time, as outlined by Science (2005), is understanding the origins of human culture. Our culture is one of the most defining features of what makes us human and differentiates us from other animals.
As we cannot go back in time to observe early hominin behaviour, our closest living relatives, chimpanzees, provide a valuable source of insight into how our culture may have started, and cognition behind the evolution of early human behaviour and material culture. Therefore, many researchers study chimpanzee behaviour to draw insights into our culture and that of other animal species.
Despite the long-standing research effort into chimpanzee behaviour, debate still remains over how their behaviours first emerge in naïve individuals. Our research focuses on experimentally testing the individual and social learning skills of both human and non-human primates in an effort to further understand how these behaviours emerge across the species.
Experimentally testing chimpanzee tool-use emergence
Our recent paper: ' Spontaneous reoccurrence of "scooping", a wild tool-use behaviour, in naïve chimpanzees ' published in the journal PeerJ this September describes the results of an experiment into the individual learning capabilities of chimpanzees. We provided naïve chimpanzees (who had never seen the wild behaviour before) with all the materials of algae scooping. Wild chimpanzees in Bossou, Guinea, routinely practice this behaviour.
The chimpanzees in our study were able to reinnovate the same technique as their wild counterparts, despite never having seen the scooping actions before. From these results, we concluded that 'scooping' is a behaviour within chimpanzees 'zone of latent solutions' (ZLS) or their pre-existing behavioural repertoire (Tennie et al., 2009). Behaviours within the ZLS of a species do not necessarily require social learning to emerge.
Chimpanzee culture
Since Jane Goodall's (1985) first report on chimpanzee's tool-use behaviours in the wild, many have argued that chimpanzees possess 'culture'. The differences in tool-use behaviours observed across wild chimpanzee populations (mapped most extensively in Whiten et al., 1999; 2001) that cannot be explained via genetic or ecological differences have been heralded as evidence of chimpanzees socially learning their population-specific behaviours from each other. This suggests that chimpanzee culture depends on social learning to emerge in naïve individuals.
Our recent paper on the individual learning of one of these presupposed 'cultural' behaviours sparked discussion. It goes against the widespread theory that social learning is absolutely necessary for naïve chimpanzees to reinnovate these behaviours. However, one common misunderstanding about the ZLS theory and our paper is that we by no means negate that chimpanzees have their own form of culture. Rather, we argue that social learning is not necessary for tool-use behaviours to emerge. What our paper suggests is that chimpanzees do not have to rely on culture, i.e. on social learning, for the latent behaviours that are expressed by naïve individuals. Thus, chimpanzees can (and, as we show, do) reinnovate tool-use behaviours when placed in the right ecology (amongst other factors) without having to socially learn the behaviour.
The role of social learning in chimpanzee culture
Although the behaviours do not depend on social learning, these processes help create the small differences in behaviours observed across chimpanzee populations in the wild. This can happen through stimulus enhancement, where observing another interacting with an object attracts an individual to it. For example, imagine a chimpanzee that has never scooped for algae before finds the debris of another chimp's scooping stick. Social learning processes will make it more likely for the naïve chimpanzee to also use a stick for the same behaviour. This way the frequency of the behaviour is socially (culturally) increased. This does not, however, mean that chimpanzees cannot spontaneously pick up a stick to scoop algae without first seeing another individual practice the behaviour (as we demonstrated in our study).
One common assumption for chimpanzee (and indeed other animal) behaviours is that if there are multiple ways to reach the same end product, at least one of these ways has to be socially transmitted. We do not agree with this view. In fact, multiple ways of dealing with the environment can all be latent solutions. Again, social learning can then harmonize frequencies of one variant within a population. But it could also have been the other, if it had started differently. As such, small differences in tool choice, such as using a wooden or stone hammer for nut cracking, can be within chimpanzees' ZLS. However, social information influences which behaviour is more likely to be expressed.
The difference between human and chimpanzee culture
Thus, social information influences chimpanzees, and subsequently clearly possess culture. However, the big difference between modern human and chimpanzee culture is the degree of reliance on social learning. Modern human culture relies on high-fidelity social learning processes such as imitation and teaching. After all, a single human couldn't reinnovate (without help) most of the products that surround us today, such as the technology you are reading this from. Conversely, all chimps could reinovate chimpanzee culture on the spot.
Although we argue that modern human and chimpanzee cultures are fundamentally based on very different mechanisms, it is important to note that humans also possess a ZLS. In fact, humans also have some basic tool-use behaviours that they can also reinnovate without social information. Reindl and colleagues (2016) presented naïve children with basic tasks and found that they spontaneously used tools to solve them. For example, the children used a stick to retrieve pom-poms from a tube without having the solution to demonstrated beforehand.
However, the difference between our ZLS and that of other animals is that we can go (and have gone) far beyond our ZLS by imitating and learning from each other, ultimately creating the extraordinary and diverse culture that surrounds us today.
References
Kummer H, Goodall J. (1985). Conditions of Innovative Behaviour in Primates. Philosophical Transactions of the Royal Society of London. Series B.
Reindl E, Beck SR, Apperly IA, Tennie C. (2016). Young children spontaneously invent wild great apes' tool-use behaviours. Proceedings of the Royal Society B, 283. Doi: 10.1098/rspb.2015.2402.
Tennie C, Call J, Tomasello M. (2009). Ratcheting up the ratchet: On the evolution of cumulative culture. Philosophical Transactions of the Royal Society, 364, 2405-2415. Doi: 10.1098/rstb.2009.0052.
Whiten A, Goodall J, McGrew W, Nishida T, Reynolds V, Sugiyama Y, Tutin C, Wrangham W, Boesch C. (1999). Cultures in chimpanzees. Nature, 399, 682-685. Doi: 10.1038/21415.
Whiten A, Goodall J, McGrew WC, Nishida T, Reynolds V, Sugiyama Y, Tutin CEG, Wrangham RW, Boesch, C. (2001). Charting cultural variation in chimpanzees. Behaviour. 138, 1481-1516. Doi: 10.1163/156853901317367717.
