Chimpanzees spontaneously reinnovate tool use behaviors: implications for early hominin behavior and culture.

by Alba Motes Rodrigo

Every one of us walks on the shoulders of giants: all human behavior is based on knowledge gathered by our predecessors. This cultural intelligence is what allowed us to be ubiquitous on this planet, and soon enough, outside of it.  But how did we end up here? When did we start collecting, modifying and accurately transferring the knowledge that constitutes modern human culture?

Technological artifacts (or tools) are currently considered the oldest instances of this special variant of culture. These tools come in three flavors: stone tools, bone tools and wooden tools (as well as marks left by tools, which are rare). If these tools are truly the product of modern-like cultural processes, this would mean that the knowledge about how to use or produce them needed to be acquired (copied) from someone else. Consequently, if these tools are “cumulatively cultural” (i.e., in the sense that we understand modern human culture today), no isolated individual could have spontaneously acquired the knowledge necessary to make and use these tools.

Members of our research group as well as researchers from institutes in Oslo (Norway), Linköping (Sweden) and Wisconsin-Madison (USA) conducted several experiments recently published in PLOS ONE and the American Journal of Primatology (AJP) with our closest living relatives, who also produce and use a multitude of tools: chimpanzees. In these studies we tested if we could find reinnovations (Bandini and Tennie 2017) of hominin and wild chimpanzee behaviors in naive captive chimpanzees i.e. those that had never performed or been exposed to these behaviors.

In the first set of experiments (Motes-Rodrigo et al. 2019 PLOS ONE), we tested the ability of two groups of chimpanzees to use tools to extract food buried underground. The results from these experiments are particularly important because this is the first time that this behavior (the use of tools to excavate buried food pieces simulating roots and tubers) has been directlyobserved and recorded. Previous reports of this behavior came from populations that are not habituated to humans, and therefore chimpanzees had never been directly observed excavating before. In this experiment, the chimpanzees also collected their own tools to excavate.

In the second experiment (Bandini and Tennie 2019 AJP), we tested the ability of several groups of chimpanzees to use tools to pound and extract food from a container. Without ever seeing another individual using the tools for these purposes, chimpanzees in most groups tested, spontaneously used stick tools to solve the tasks. As before, the chimpanzees collected their own tools and brought the to the testing area.

We can be certain that at least the first chimpanzee in each of the groups tested where the target behavior was reinnovated, did so spontaneouslyi.e. without the need to see any kind of demonstrations. That is, social learning of any kind (including action copying) proved unnecessary to explain the formof these behaviors! These results show that some hominin and wild chimpanzee behaviors do not rely on copying to be acquired by naïve individuals. These studies contribute new data to the growing body of evidence showing that many behavioral forms previously considered cultural (in the sense of modern-culture) can actually be acquired relying solely on individual learning. This does not exclude a role of social learning, however, as some non-copying variants of low fidelity social learning are likely to play an important role in the increase in frequency of target behaviors. That the chimpanzees in this study did not require to observe any models, further means that we should be more cautious in assigning cultural properties to all early hominin and wild chimpanzees technological behaviors. As more and more studies of this kind are published, it becomes clearer that chimpanzee, and  perhaps now also early hominin, cultures are actually likely different from modern-human cultures. Their cultures (like so many others in the animal kingdom) use social learning to increase the frequencies of behavioral forms – but the behavioral forms themselves do not require any variant of social learning mechanisms. This seems to be the strongest difference to human culture – where copying is necessary.

References

Motes-Rodrigo, A., Majlesi, P., Pickering, T.R., Laska, M., Axelsen, H., Minchin, T. C., Tennie, C. and Hernandez-Aguilar, R. A. 2019. Chimpanzee Extractive Foraging with Excavating Tools: Experimental Modeling of the Origins of Human Technology. PLoS ONE 14(5): e0215644. 

Bandini, E., & Tennie, C. 2017. Spontaneous reoccurrence of “scooping”, a wild tool-use behaviour, in naïve chimpanzees. PeerJ. 5, e3814.

Bandini, E & Tennie, C. 2019. Individual acquisition of ‘stick pounding’ behaviour by naïve chimpanzees. American Journal of Primatology. e22987 

Media coverage:

IFLS: https://www.iflscience.com/plants-and-animals/captive-chimps-learn-a-digging-behavior-once-thought-unique-to-humans-and-other-hominins/

New Scientist: https://www.newscientist.com/article/2204102-chimps-that-mash-potatoes-challenge-our-understanding-of-tool-use/?utm_term=Autofeed&utm_medium=SOC&utm_source=Twitter#Echobox=1558465877

The musings of a formerly confused cultural evolutionist

Written by: Damien Neadle and Claudio Tennie

Culture is all around us, from the device that you are seeing/hearing this on to the very words I am using. However, it is a rather slippery fish to grasp and it can be difficult to nail down exactly what culture is.

Thought exercise

When I say “culture” what do you think of? I expect that this will vary depending on who you are: a biologist might think of something close to the definition provided by the Oxford English Dictionary (2019):

“The cultivation of bacteria, tissue cells, etc. in an artificial medium containing nutrients”

An anthropologist might think of another part of the Oxford English Dictionary (2019) definition:

“The arts and other manifestations of human intellectual achievement regarded collectively; The ideas, customs, and social behaviour of a particular people or society”

A comparative psychologist, like myself, might envisage something altogether more simple. For example, when I hear culture, I think of a family of chimpanzees sitting together cracking panda nuts in Taï Forest, Côte d’Ivoire. These different ways to perceive culture – and their contrast to the way I think of culture – frequently presents a problem for me when I am talking to people about culture in non-humans.

My problem

I often find myself hesitating to even use the term culture at all because, for some, it is synonymous with human culture, which is special – human culture is “cumulative” (Tomasello, Kruger, & Ratner, 1993). Whilst there are debates as to whether at least some non-human cultures also qualify as cumulative (see, for example, Schofield, McGrew, Takahashi, & Hirata, 2017), most would agree, human culture is special – even if that means that it simply often is cumulative (instead of always).

Therefore, my coauthors and I found ourselves seeking another term for the interesting processes that chimpanzees (and other non-humans) engage in regularly; in this post, I will be talking you through our logic in selecting a term and the pitfalls and advantages that the possible definitions contain.

The options

In the nineties, there was a call for a distinction between cultures and traditions – the difference between these terms was a topic of significant debate (see Galef, 1992); Galef concluded that a tradition is a behaviour type that is somehow acquired, at least in part, by social learning mechanisms, other than imitation ¹ or teaching. According to Galef, culture instead relies on imitation and teaching. Galef (and other early researchers e.g., Jane Goodall) should be applauded for their forward thinking “splitter” mentality – but, alas this distinction did not catch on as much as some may have preferred.

Somewhat expectedly, there is a degree of pushback within the field from what Galef termed “lumpers”, those who fail to see a distinction between cultures and traditions or may wish to attribute culture to non-humans. Culture, after all, has a nice ring and a high impact factor attached to it, and so, taking it away from many other animals has far-reaching consequences.

In a well-cited paper a group of field researchers from research sites across Africa sat down to compile their observations to generate a tentative list of the repertoire of wild chimpanzee behaviours; crucially, they divided up the repertoires by frequencies and by population (Whiten et al., 1999). This allowed them to produce a derived list from the behaviours themselves, namely a list of putative cultural traits of chimpanzees (see also Whiten et al., 2001). The logic being that population level (geographical) differences in behavioural repertoires might be due to cultural forces (this is similar logic to that employed in anthropology, for example, the different human cultures of eating food with hand, versus chopsticks versus cutlery etc). However, a factor missing from these reports (which was not identifiable with this so-called “method of exclusion”) was to pinpoint the exact underlying social learning mechanism(s). Indeed, even non-social learning mechanisms and that Galef would not even have counted as underlying traditions (let alone culture) often could not be excluded (Langergraber et al., 2011).

In using terms such as “culture” to describe these patterns of behaviour we, as a field, left these findings open to misinterpretation. In the original paper (Whiten et al., 1999, p. 685), it was directly claimed to be “difficult to see how such behaviour patterns could be perpetuated by social learning process simpler than imitation”, whilst useful, the data in this study do not allow the veracity of such a claim to be tested.

In examples like these, which are frequent, we can see how the current use of the term “culture” has become detached from that of Galef. Again: for Galef, for something to be called cultural it is required that the trait is indeed underlain by imitation. With this in mind, the evidence for chimpanzee imitation is all too often lacking; claims of imitation are usually misnomers or failures to control for variants of social learning other than imitation. Tests of ‘pure’ imitation (where a task cannot be solved by any social learning mechanisms other than one including action copying) reliably yield negative results (Clay & Tennie, 2017; Tennie, Call, & Tomasello, 2012; Tomasello et al., 1997). In other words, apes do not spontaneously ape (i.e., imitate). Hence, following the logic of Galef, the chimpanzee behavioural differences between populations are certainly interesting, but they are not cultural as they are not shown to be based on imitation – we would need to conclude that we have here evidence for chimpanzee traditions instead.

This debate has raged for some time, with adherents on both sides – and even we ourselves, one of the major objectors to ‘lumping’ are tired of it. But an alternative seems possible – and this is what we recently proposed (Neadle, Allritz, & Tennie, 2017). The solution is to simplify the definition of culture to the bone – we merely add qualifiers to the term, to not loose precision. That way, we hopefully can focus on collecting and comparing data rather than to waste resources fighting definitions.

Our solution

We proposed the most minimal definition of culture that would seem possible. The bar for any animal to become cultural has been set intentionally low by our definition. This is so as not to alienate researchers from the start (if you like your animal species to have culture – while empirical evidence is still necessary even in our definition – the empirical test can be very easily made) and to allow the widest possible net to be thrown out to find animal culture. Arguably the latter is the best approach to enable us to detect general evolutionary patterns.

We, therefore, proposed the “minimal culture” definition: This definition directly equates the presence of any variant of social learning mechanism in any species with culture (Neadle et al., 2017). “Minimal” is simply part of the name of the definition and need not be added in front of the term culture. And so, if you find social learning of any flavour in your study species – congratulations, you have found culture. Crucially, our definition does not require that a specific social learning mechanism (such as imitation) is at play. In fact, a behaviour can be considered cultural – under this definition, if social learning is shown to have any influence at all. For example, if a social learning mechanism is at play that merely facilitates/catalyses the expression/frequency of a behaviour – that’s fine, and is, therefore, culture (compare also Tennie, Call, & Tomasello, 2009).

But with this new, low bar, we have not only rid the debate of the need to show imitation before one can talk of (minimal) culture (others have done the same in their own definitions for similar processes: e.g. Socially Mediated Learning; Caldwell & Whiten, 2002). Here, we took the lesson from the past – these fights about what is and isn’t cultural proved unnecessary bonfires of resources. And so, we designed our definition to really and truly be minimal – there is no additional baggage. In other words, social learning is culture. Thus, by using our definition, there is no need to argue whether, additionally, the behaviour itself is copied, whether it lasts so and so long, whether it appears in at least these many individuals etc.

It’s pure and simple and that’s why we like it. We hope you do, too.

Now, can we please use all our concentration on actual data, and stop fighting over words?

¹ In this context, imitation is the copying of actions (Whiten et al., 2004), this is distinct from copying only the results of these actions – termed emulation. Yes reader, I know, term overload, but bear with me here! I am going to focus on imitation in this post – teaching is a whole new kettle of fish!

References
Caldwell, C. A., & Whiten, A. (2002). Evolutionary perspectives on imitation: Is a comparative psychology of social learning possible? Animal Cognition, 5(4), 193–208. https://doi.org/10.1007/s10071-002-0151-x
Clay, Z., & Tennie, C. (2017). Is Overimitation a Uniquely Human Phenomenon? Insights From Human Children as Compared to Bonobos. Child Development, 00(0), 1–10. https://doi.org/10.1111/cdev.12857
Galef, B. G. (1992). The Question of Animal Culture. Human Nature, 3(2), 157–178.
Langergraber, K. E., Boesch, C., Inoue, E., Inoue-Murayama, M., Mitani, J. C., Nishida, T., … Vigilant, L. (2011). Genetic and ‘cultural’ similarity in wild chimpanzees. Proceedings of the Royal Society B: Biological Sciences, 278, 408–416. https://doi.org/10.1098/rspb.2010.1112
Neadle, D., Allritz, M., & Tennie, C. (2017). Food cleaning in gorillas: Social learning is a possibility but not a necessity. PLoS ONE, 12(12), e0188866. https://doi.org/10.1371/journal.pone.0188866
Schofield, D. P., McGrew, W. C., Takahashi, A., & Hirata, S. (2017). Cumulative culture in nonhumans: overlooked findings from Japanese monkeys? Primates, (0123456789), 1–10. https://doi.org/10.1007/s10329-017-0642-7
Tennie, C., Call, J., & Tomasello, M. (2009). Ratcheting up the ratchet: on the evolution of cumulative culture. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 364(1528), 2405–2415. https://doi.org/10.1098/rstb.2009.0052
Tennie, C., Call, J., & Tomasello, M. (2012). Untrained Chimpanzees (Pan troglodytes schweinfurthii) fail to imitate novel actions. PLoS ONE, 7(8). https://doi.org/10.1371/journal.pone.0041548
Tomasello, M., Call, J., Warren, J., Frost, T., Carpenter, M., & Nagell, K. (1997). The Ontogeny of Chimpanzee Gestural Signals: A Comparison Across Groups and Generations. In S. Wilcox (Ed.), Evolution of Communication (pp. 224–259). Amsterdam, The Netherlands: John Benjamins.
Tomasello, M., Kruger, A., & Ratner, H. (1993). Cultural Learning. Behavioral and Brain Sciences, 16, 495–552. https://doi.org/10.1017/S0140525X0003123X
Whiten, A., Goodall, J., Mcgrew, W. C., Nishida, T., Reynolds, V., Sugiyama, Y., … Boesch, C. (1999). Cultures in chimpanzees. Nature, 399, 15–18.
Whiten, A., Goodall, J., Mcgrew, W. C., Nishida, T., Reynolds, V., Sugiyama, Y., … Boesch, C. (2001). Charting Cultural Variation in Chimpanzees. Behaviour, 138(11), 1481–1516.
Whiten, A., Horner, V., Litchfield, C. a, & Marshall-Pescini, S. (2004). How do apes ape? Learning & Behavior, 32(1), 36–52. https://doi.org/10.3758/BF03196005

Conformity in wild vervet monkeys? Possibly not.

Comment on van de Waal, E., Borgeaud, C., & Whiten, A. (2013). Potent social learning and conformity shape a wild primate’s foraging decisions. Science, 340(6131), 483-485.

Written by:

Claudio Tennie, Julia Fischer, Daniel B. Haun & Bennett G. Galef

 

[This was written, submitted and appeared on Science magazine online at the time – but somehow its now lost there. So, rather than resubmit etc etc its now simply here]

 

The conclusion [1] that vervets exhibit “conformity” is, we believe, premature (even though methodologically this study is superior to a previous study making a similar claim in chimpanzees [2]).

Conformity – adjusting ones behaviour to that of a majority – characterizes human cultural learning. Consequently, conclusive evidence of conformity in a non-human primate would increase understanding of the evolution of human culture.

In [1], groups of wild monkeys were trained to avoid one of two different foods. Males subsequently migrating between groups with different food preferences reversed their food choices to match that of the group into which they migrated. The authors concluded that the migrants conformed to the majority [1].  However, socially induced biases other than conformity can account for the reported effect.

Norway rats trained to avoid one of two foods preferred that food after interacting with a single conspecific eating it [3]. Similarly, migrating vervet males might have copied the food choices of a few individuals (e.g females [4])– or even a single other individual (e.g. a dominant) rather than copied the majority. Consistent with the latter hypothesis, the single migrant that did not change food preference was immediately of highest rank in the group he joined [1]. In any case, there is no need to invoke “conformity” to explain the behaviour of migrating males [5, 6].

While it is indeed interesting that social learning can result in stable variation in food choices of vervet social groups, the mechanisms of such social learning may well differ from those supporting analogous behaviour in humans. “Conformity,” particularly normative conformity [7], remains to be demonstrated in non-human primates.

 

1. van de Waal, E., Borgeaud, C. and Whiten, A. (2013). Science 340, 483-485.

 

2. Whiten, A., Horner, V. and de Waal, F. B. M. (2005). Nature 437, 737-740.

 

3. Galef, B. G. and Whiskin, E. E. (2008). Anim. Behav. 75, 2035-2039.

 

4. van de Waal, E., Renevey, N., Favre, C. M. and Bshary R. (2010). Proc. R. Soc. B 277, 2105-2111.

 

5. Haun, D. B., Leeuwen, E. J. V. and Edelson, M. G. (2013). Dev. Cogn. Neurosci. 3, 61-71.

 

6. Leeuwen, E. J. V. and Haun, D. B. (2013). Evol. Hum. Behav. 34, 1-7.

 

7. Deutsch, M. and Gerard, H. B. (1955). J. Abnorm. Soc. Psych. 51, 629-636.

Open Science Series – Open Access

Damien Neadle

Open science is a term that we hear a lot as academics, however, what exactly does it mean? In this blog series I will discuss some of the most important aspects of open science, including access, data and good practice. As our lab becomes ever more involved with the open science movement, we encourage open science (in all its forms) in our members and those we work with. We are keen to implement changes in our work as the movement progresses.

Open Access

This is probably the most common form of open science. One may often hear about people publishing Open Access, but what does this mean? Well, there are three (main) levels of Open Access:  green, gold and platinum.

Green is the “lower” level form of Open Access; usually articles with green Open Access are published in a more traditional (subscription or pay-to-view) journal. However, the author retains the right to place their work (or at least a non-final version of it) on some form of repository – institutional or subject specific – after an embargo period has passed. The OpenDOAR project allows you to search for a suitable repository for your paper (http://v2.sherpa.ac.uk/opendoar/). Green Open Access usually doesn’t come with any additional charges. Whilst this is a substantial “improvement” over the traditional journal model – as the science can be disseminated publicly for free – there are drawbacks. For example, as the version of the document that is permitted in the repository is not the published version of the manuscript, it can often lack the polishing and clarity that a formal copy editing process provides. See the SHERPA project for a bank of information of each journal’s self-archiving policies (http://www.sherpa.ac.uk/romeo/index.php). In addition, it may be that the version placed in the repository is not the final version (this is the so-called “pale green” option), so minor errors may still be present. Despite its drawbacks, there is really no reason why any journal/author should not facilitate green Open Access at the very least. It is a low/no cost (the only cost being to the repository) method of scientific dissemination.  However, some authors (myself included)  remain dissatisfied with the limitations of green Open Access, as a result, one may turn to gold Open Access.

Gold Open Access is (or at least was), as the name suggests, the gold standard in Open Access content. This is a form of Open Access where the onus is on the publishers themselves to host the articles in a manner where they can be freely accessed. The final article is usually published under a form of licence agreement that allows free dissemination, under creative commons licence. Journals that offer gold Open Access fall into one of two categories, pure Open Access journals and hybrid journals. A pure Open Access journal only publishes articles using gold Open Access; e.g., PLoS ONE. Meanwhile, hybrid journals are traditional (subscription model) journals that offer gold Open Access as an option. The drawback with gold Open Access is that it comes with a large fee that must be paid by the author. Do not despair though, many large universities have an Open Access budget that is designed to cover these fees – research suggests that as many as 88% of these charges are either paid by an institution or are waived by the journal (https://arxiv.org/abs/1101.5260).

One must recognise, that a large fee may limit which authors can publish using gold Open Access. As a result, the platinum option is more recently being incorporated into the models of many journals dedicated to open science. Platinum Open Access is referred to as a few different things – diamond Open Access, universal access and universal Open Access being a few examples – they are all the same model. Platinum Open Access is simply an evolution of gold, whereby the article processing fee is removed, the costs being covered by a 3rd party (often not for profit) or the journal themselves. This, therefore, allows the material to be published without barriers. Do not assume that all gold level Open Access publishers operate on a “author pays” model, there are many models that also allow the publishers to remove article processing fees (http://oad.simmons.edu/oadwiki/OA_journal_business_models). As many as 70% of pure Open Access journals charge no author fees (https://dash.harvard.edu/handle/1/4552050), however, the large, high impact, journals are yet to adopt this standard on a large-scale.

The full spectrum of Open Access.

A Proposal for Systematic Replication in Psychology

Written by Claudio Tennie and Richard Moore

This blog post is in response to a recent target article on the replication crisis

Zwaan, R. A., Etz, A., Lucas, R. E., & Donnellan, M. B. (2017). Making replication mainstream. Behavioral and Brain Sciences, 1-50. https://doi.org/10.1017/S0140525X17001972

In the face of the continuing so-called replication crisis, we must aim to fix the system, and to bring scientific research back on track – both with respect to the integrity with which it is conducted, and the faith that others have in it. We therefore strongly agree with the arguments and approach as presented by Zwaan et al. (2017 – see above). Here, we suggest a systematic extension of their proposed program – with a focus on the field of psychology.

We propose to extend the proposals of Zwaan et al. in three ways: (1) to mark differences between replicated and non-replicated work in writing, (2) to use patterns arising from systematic replication to reinforce a just system of reputation management in psychology, and (3) to describe an outline of how a systematic replication system could be installed.

(1) Given the unsatisfactory proportion of psychological findings that currently do not replicate, we as a field could mark this verbally in future manuscripts (and journals/editors could begin to require this). Where authors’ key claims rely on findings that have not (yet) been replicated, they should be encouraged to acknowledge this explicitly in in text citations (e.g. “Smith et al. 2000 – currently awaiting replication”). This system might be extended to count only replications from outside the original group (e.g. “Smith et al. 2000, 2001 – currently awaiting independent replication”). Additionally, where key claims have been subjected to failed replications of which the authors are aware, they should be expected to acknowledge this, and discuss the failure to replicate.

Journals should be encouraged to facilitate authors’ tracking of replication attempts, by systematically updating manuscript websites to link to ongoing, successful, and unsuccessful replication attempts. Successful replications could then be marked and flagged, so that authors could easily track the reliability of the findings they cited (where originals authors had contested unsuccessful replications, these too could be linked from online publication sources.)

(2) While we would like to emphasise the importance of replication attempts, authors should be protected from the possibly negative consequences of single/few failed replications – since inevitably, the findings of honest researchers will sometimes fail to replicate. By adopting a policy of systematic replication attempts, the field of psychology will benefit from both a more reliable exposure of persistent fraud (which we take as self-eminently the most harmful kind) and, at the same time, learn to downplay the role of occasional failures to replicate for personal careers. Where replications are systematic, only if an individual’s work systematically failed to replicate would their reputations suffer. Within such a system, researchers tempted to take shortcuts on their data sets would know they increase their risk of exposure (or reputation drain), and honest researchers would rest assured that overall the reliability of their work would shine through. Of course, underlying reasons for systematic failure to replicate might include unintentionalprocesses (e.g., where a whole field of study had adopted substandard research methods (as detailed by Zwaan et al. (2017))) – but systematic replications could here lead to the adoption of new, more appropriate standards of rigour. In such cases, replications failures would not automatically lead to suspicions of dishonesty, but instead would highlight methods in need of repair.

(3) We propose the ‘PhD Replication Project’. The most straightforward way to encourage systematic replication would be to assign a standard requirement for replicating one finding in the literature to every PhD candidate in psychology. From a centrally constructed database, students would be permitted to choose which currently unreplicated studies to attempt to replicate, as this related to their own research interests. Therefore replication attempts would nonetheless contribute to the foundations of their own PhD research, and young students would not be unfairly burdened with the task of rectifying others’ mistakes.

If this ’PhD Replication Project’ proposal were adopted systematically, individual PhD students would not suffer relative to others. Additionally, while replications in some fields likely take longer than in others, relative publications rates between subfields should not be affected. Of course, PhD student replications should be supplemented by larger replication projects, which could be used for particularly large and demanding replication attempts. But larger projects could also be broken down into smaller parts, suitable for replication attempts by multiple PhD students.

Pressure to make PhD-granting institutions comply with this system could come from grant agencies and governmental resources, who could make it a prerequisite of research funding that PhD scholarships participate in the replication project. If all PhD students were required to replicate, the foundations of any active field of research would rapidly be secured – with the more active fields benefitting most rapidly.

 

How clean is your food?

Written by: Damien Neadle

This post will serve as a brief taster and summary of the main conclusions for the following paper.

Neadle D, Allritz M, Tennie C (2017) Food cleaning in gorillas: Social learning is a possibility but not a necessity. PLoS ONE 12(12): e0188866. https://doi.org/10.1371/journal.pone.0188866

Everything around you right now is the product of culture, from the screen that you are reading this on to the chair that you are sat on; however, the key difference (arguably) between the culture that created these, and the culture that our non-human cousins display is the notion of accumulation (Tomasello, 1998). The concept of cumulative culture (outlined by Tomasello, Kruger, & Ratner, 1993) is one for another post, here we are interested in the culture displayed elsewhere in the animal kingdom.

In my recently (and first) published paper we provide evidence which challenges the notion that cultures require copying social learning to occur. Instead we suggest, in line with previous work from our research group (Bandini and Tennie 2017), that while social learning is responsible for the frequency of behaviours in a population, individual learning is responsible for the emergence of the form, at least in non-human primates.

To avoid confusion between traits that require social learning to emerge (i.e., culture-dependent traits) and those that do not, we introduced a new “soft” definition of culture that ascribes a lower level of culture to any behaviour where social learning is present, in any form. We apply this definition to our example of food cleaning, which had recently been dubbed a putative cultural trait. However, this soft culture concept can be applied to many other great ape behaviours such as algae scooping, a behaviour that is individually reinnovated, but which expression may be facilitated by social learning (Bandini & Tennie, 2017).

Given how common a behaviour such as food cleaning is in the animal kingdom (Neadle, Allritz, & Tennie, 2017), it was unlikely that social learning was required for its emergence. In fact, our data combined with that of Robbins et al (2016), show that all western lowland gorillas, in which food cleaning has been studied, have shown evidence of performing this behaviour. Consequently, food cleaning can be considered as a species universal (Whiten et al., 2001). Thus, our results show that even species universals (that are facilitated by social learning) are included in the “soft” culture definition.

The finding that social learning is not necessary for the emergence of food cleaning lends support to the Zone of Latent Solutions hypothesis (Tennie, Call, & Tomasello, 2009), and suggests that the null hypothesis for non-human animal behaviour should be redirected to assume that individual learning is the default explanation for the emergence of behaviors in primates.

Chimpanzees can reinvent their culture

Written by: Elisa Bandini

The following post was originally posted on http://www.evoanth.net/2017/11/02/chimps-reinvent-culture/ as an assessment of some of the misconceptions of our recent paper; Bandini & Tennie. 2017. ‘Spontaneous reoccurrence of “scooping”, a wild tool-use behaviour, in naïve chimpanzees’

Overview

One of the top 125 questions of our time, as outlined by Science (2005), is understanding the origins of human culture. Our culture has been argued to be 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 (in particular tool-use) 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, a behaviour observed in wild chimpanzees in Bossou, Guinea.

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, therefore suggesting 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 as it goes against the current widespread theory that social learning is absolutely necessary for these behaviours to be reinnovated by naïve chimpanzees. However, one common misunderstanding about the ZLS theory and our paper is that whilst we argue that social learning is not necessary for tool-use behaviours to emerge, we by no means negate that chimpanzees have their own form of culture. Instead, 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 (such as stimulus enhancement, where individuals are attracted to a specific object by observing another individual interacting with that, or a similar, object) help create the small differences in behaviours observed across chimpanzee populations in the wild.

For example, if a chimpanzee that has never scooped for algae before comes across 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: 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 a 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). And so, small differences in tool choice (e.g. using a wooden or stone hammer for nut cracking) can be within chimpanzees ZLS, but social information influences which behaviour is more likely to be expressed.

The difference between human and chimpanzee culture

Thus, chimpanzees are also influenced by social information, and subsequently clearly possess culture. However, the big difference between modern human and chimpanzee culture is the degree of reliance on social learning: whilst modern human culture relies on high-fidelity social learning processes such as imitation and teaching (indeed, most of the products that surround us today, such as the technology you are reading this from, could not be reinnovated by a single individual on the spot), chimpanzee culture can be reinnovated on the spot by all individuals.

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 children with novel tool-use tasks and found that the naïve children spontaneously used tools to solve basic problems (such as using a stick to retrieve pom-poms from inside a tube) without needing the solution to be 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.

Elisa Bandini

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.