Cultured chimps pass on new traditions between groups


Blogging on Peer-Reviewed ResearchFor humans, our culture is a massive part of our identity, from the way we dress, speak and cook, to the social norms that govern how we interact with our peers. Our culture stems from our ability to pick up new behaviours through imitation, and we are so innately good at this that we often take it for granted.

Chimpanzee groups can learn new traditions from each other.We now know that chimpanzees have a similar ability, and like us, different groups have their own distinct cultures and traditions.

Now, Andrew Whiten from the University of St Andrews has published the first evidence that groups of chimpanzees can pick up new traditions from each other. In an experimental game of Chinese whispers, he seeded new behaviours in one group and saw that they readily spread to others.

Many animals have their own cultural traditions. Songbirds, for example, copy their parents' melodies, and small variations lead to groups with different dialects. But chimpanzees have by far the richest cultures so far observed.

These scope of their culture first came to light in 1999, when Whiten, together with Jane Goodall and others, carefully documented at least 39 cultural behaviours among wild chimpanzees. Many of these were a matter of course in some populations, but completely absent in others.

Some groups use sticks to extract honey, others use them to retrieve marrow from bones, and yet others use them to fish for ants. Some get attention by rapping their knuckles on a branch, while others noisily rip leaves between their teeth. Some groups even have a rain dance.

Whiten has previously published three studies which demonstrated different sides of chimp cultural transmission. The first showed that trained individuals can spread seeded behaviours within a group. The second showed that cultures trickle through the generations as parents teach their children new behaviours. And the third showed that arbitrary conventions such as gestures and displays can spread as easily as skills involving tool use.

Now, together with an international team of researchers from the University of Texas and Yerkes National Primate Research Center, including primate expert Frans de Waal, Whiten has produced the first experimental evidence that cultural transmission can happen between different groups.

Whiten worked with six groups of captive chimps, each consisting of 8-11 individuals. They lived in large but separate enclosures arranged in two rows of three and each group could observe its neighbours, but not interact with them.

Whiten trained one chimp from groups one and four to solve two difficult tasks - the 'probe task' and the 'turn-ip' task - in order to get some food hidden inside a box. Each chimp was taught to use a different technique.

The probe taskIn the probe task, the chimp could move a lever at the top of the box to open a hatch, and use a stick to impale the food (A). Alternatively, it could use another lever at the side to lift an opening, giving it enough room to manoeuvre a stick inside and push the food out (B).

The turn-ip taskIn the turn-ip task (C), food items were dropped down a pipe, where they were blocked by a disc. The disc had a hole in it, that would allow the food to fall through when it was properly aligned. The chimps could turn the disc either by rotating an exposed edge or using a ratchet. Once the food dropped through, the chimps could get at it by pressing or sliding one of two different handles.

Once the student chimps had mastered their new methods, they were returned to their respective compounds and the whole group was allowed to try its hand at the tasks. Before the training, none of the chimps managed to successfully get at the food. But after just one chimp was taught the technique, most of the others in the group quickly picked it up.

The boxes were then moved to a different position, where chimps from the second pair of groups could watch chimps from the first pair solving the task. After a time, it was moved to another position where the third pair of groups could watch the second one.

Whiten found that the techniques were accurately and quickly transmitted between the different chimpanzee groups. His experiment clearly shows that chimps have an immense capacity for learning new behaviours from their peers. They do this accurately and different groups can acquire and maintain several varied cultural traditions.

Different chimpanzee groups have distinct cultural traditions.In light of this evidence, the regional behaviour patterns seen in chimp groups across Africa are, without a doubt, the result of cultural transmission. In the wild, rival groups are often hostile towards each other and it is unlikely that chimps sit down in jungle conferences to share new ideas. But females do move between groups and Whiten believes that they carry new cultural traditions with them.

How exactly the new behaviours spread is still a matter for debate. Some scientists have suggested that the chimps learn by 'emulation', meaning that they focus on the results of actions rather than the actions themselves. But other studies found that chimps don't respond to 'ghost' lessons, where task machinery is operated by remote and not by another chimp.

The most likely explanation is that chimps imitate the actions of other chimps and are very good at learning from each other. In all likelihood, the common ancestor that we share with chimps had the same ability, and also had strong cultural streams running through its populations.

Reference: Whiten, Spiteri, Horner, Bonnie, Lambeth, Schapiro & de Waal. 2007. Transmission of multiple traditions within and between chimpanzee groups. Current Biology 17: 1-6.

Images: Image of experimental apparatus taken from Cell Press.

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Sounds pretty simple to me, monkey see, monkey do, short term memory to long term memory, and wala.

Kids' culture is transmitted the same way. Individual kids watch others at play to get a sense of the mood as well as the particular game and then join in. That's one of the skills that are commonly missed by socially awkward kids who join in without first observing and imitating.

So... Monkey sees monkey do, so monkey do?

Social inheritance isn't that new - ethologists, evolutionary biologists and philosophers of biology have studied it for quite a while. In fact, it's majorly important for evolution in general

I think Jablonka & Avital (in "Evolution in four dimensions" and "Behavioural Inheritance") have got it almost right in identifying four inheritance systems in nature: genetic, epigenetic, behavioural and symbolic.

Sadly though, the gene-centrism rampant since the triumph of molecular genetics means that this centrism is what is presented to the public and to students - talking about non-genetic inheritance and nongenetic factors of evolution is almost treated as heresy among some (not all, fortunately).

But it's not that hard to see how behavioural inheritance can shape evolution - the best and most abundant evidence being improvements in foraging-behaviour.

I'm sure many of you have read about the group of bottlenose-dolphins where some females had developed a way to use sponges to increase the ease and efficiency of searching for food and preparing it for ingestion, and that this behaviour is passed on vertically (from parents to offspring) among the females.

Now suppose that (as is quite evident) this behaviour actually increases the availability of nourishment for those adopting the behaviour - this lessens selection-pressure on those adopting it (and perhaps non-participating benefactors) - voila, the behaviour is selected for. Perhaps this increase in efficiency allows for larger group-sizes and/or an increase in habitat-area - leading to a new, improved (from the dolphins' point of view) stable relationship with a redefines (broader) environment... A change in the ecosystem brought about by variation and selection - i.e. evolution.

However, successful imitation learning requires quite a bit of cognitive effort, and as such is not the most basic, most easily employed way of behavioural inheritance. Cue-driven behaviour on the basis of templates often suffices for behavioural inheritance - for example, there is a group of rats living (unusually) in a forest and feeding (unsually) on seeds from cones. The latter is unusual because prying the seeds from the cones isn't easy - in fact it is so hard that no rats have been observed to be able to do it without having inherited the behaviour.

People were quick to posit imitation-learning as the factor behind this, but as it turned out, things were a little different: Mother rats began to work on the cones in their established spiral pattern, but stopped some way through, allowing their offspring to try themselves. They begin tracing the biting-pattern of the mother, following the biting-marks the mothers leave (simple cue-driven feeding behaviour) - and thus, in virtue of the feeding-attempts initiated by cues and the pattern that the template cone forces/guides them to employ, they inherit the behaviour without imitation learning, that is observation and mimicking.

However, in opposition to Jablonka & Avital, I would refrain from using the word culture in that context. Behavioural inheritance through imitation-learning and template-learning (and perhaps in other ways) is social, but not cultural.

We get a more fine-grained and useful distinction (that, as a bonus, can also apply the distinctively human aspects of social living) by only applying the predicate 'cultural' where actual, generationally stable 'externalization' happens, i.e. the production of cultural artifacts - modifications in the environment that fulfill generationally stable roles, i.e. that allow new generations to inherit complex behavioural schemata and integrate them into complex social phenomena by simply being shaped by the environment - without specifically having to learn everything through personal learning.

In any case - the dogma that every evolutionary relevant trait is inherited only through the Weissmann-bottleneck of the genes is blatantly false. This in no way detracts from the success of molecular genetics - it just shows that not everything can be usurped by it.

The literature on this is fascinating - and only through recognizing these inheritance systems can we begin to develop a real explanation for the huge difference between the complexities of human lives and that of any other animal... science, poetry, philosophy, discussions, governments, technology, uncounted social roles and empirically constitutable differences in them between people....
...sadly, many simply close their eyes to the severity of these differences because it doesn't fit into the gene-centristic view and the dogma that evolution has to be smooth so there can be no drastic differences.

Thankfully, through learning to understand behavioural and social inheritance we can begin to understand how all this fits perfectly in the theory of evolution. We can understand how language, cultural inheritance and the neuronal density and complexity of connectivity in the neocortex specifically can account for the distinctively human aspects of sociality and culture, and how language is the main catalyst for cultural evolution, explaining the evolutionary possibility for the emergence of the above mentioned distinctive aspects.

Of course, once complex social functions and social inheritance emerge in populations, ther IS a benefit for mutations that increase the efficiency of neocortical activity, as this will allow better and more flexible adaption to these social constructs, which can arise and persist even without flexible, intelligent cognition.

Still, many of those studies on animal cognition and sociality are to be taken with a grain of salt... often, interpretative inferences are made that are neither parsimoneous nor neuroscientifically plausible.

Interestingly, evolutionary theory and animal cognition-research is something where philosophers of biology have contributed majorly, where a synergetic cooperation of biologists and philosophers has helped to uncover many problems with widespread definitions of fitness and selection and with the aforementioned interpretations. Of course a good number of biologists were always careful enough to avoid the pitfalls of unparsimoneous and physiologically implausible inferences. Sadly, many biologists still ignore the contributions of philosophers, contributions which those biologists who do make the effort to understand them recognize as important and fruitful.

In any case, if you're interested in this sort of thing (social inheritance, culture etc) , I'd recommend the following literature:

Jablonka & Avital - Behavioral Inheritance
" " - Evolution in Four Dimensions
Boyd & Richerson - The Origin and Evolution of Cultures
M. Tomasello - The Cultural Orgins of Human Cognition
Hurley & Nudds - Rational Animals?

and for imitation learning and its neuroscientific basis, I'd recommend

Hurley & Chater - Perspectives on Imitation - From Neuroscience to Social Science

and in case anyone should be doubtful about or interested in the import of philosophy to evolutionary biology - the Stanford Online Encyclopedia of Philosophy has several highly interesting articles that show the relevant conceptual problems that give the issues in question a strong philosophical dimension, most notably with such concepts as fitness and selection:

They also have a general article on philosophy of biology...

Anyway - great post. It's time more people read about social inheritance!

Abb3w - precisely.

"So... Monkey sees monkey do, so monkey do?"

Actually.. this needs a little modification.
Ape sees ape do, so ape do!