Chimpanzees perform the same complex behaviors that have brought humans success
University of Oxford
image:
Adult female cracking nuts using stone tools. She is being observed by an infant female (1 year old) and a young male (8
years). Credit; Tetsuro Matsuzawa
Credit: Tetsuro Matsuzawa
More images and video available- see link in the Notes section.
A new study suggests that the fundamental abilities underlying human language and technological culture may have evolved before humans and apes diverged millions of years ago. The findings will be published 5th December 2024 in the journal PeerJ.
Many human behaviours are more complex than those of other animals, involving the production of elaborate sequences (such as spoken language, or tool manufacturing). These sequences include the ability to organise behaviours by hierarchical chunks, and to understand relationships between distantly separated elements.
For example, even relatively simple human behaviours like making a cup of tea or coffee require carrying out a series of individual actions in the right order (e.g. boiling the kettle before pouring the water out). We break such tasks down into solvable chunks (e.g. boil the kettle, get the milk and teabag, etc), composed of individual actions (e.g. ‘grasp’, ‘pull’, ‘twist’, ‘pour’). Importantly, we can separate related actions by other chunks of behaviour (e.g. you might have to stop and clean up some spilt milk before you continue). It was unknown whether the ability to flexibly organize behaviours in this way is unique to humans, or also present in other primates.
In this new study, the researchers investigated the actions of wild chimpanzees – our closest relatives – whilst using tools, and whether these appeared to be organised into sequences with similar properties (rather than a series of simple, reflex-like responses). The research was led by the University of Oxford with an international collaboration across the UK, US, Germany, Switzerland, and Japan.
The study used data from a decades-long database of video footage depicting wild chimpanzees in the Bossou forest, Guinea, where chimps were recorded cracking hard-shelled nuts using a hammer and anvil stones. This is one of the most complex documented naturally-occurring tool use behaviours of any animal in the wild. The researchers recorded the sequences of actions chimps performed (e.g. grasp nut, pass through hands, place on anvil, etc.) – totalling around 8,260 actions for over 300 nuts.
Using state-of-the-art statistical models, they found that relationships emerged between chimpanzees' sequential actions which matched those found in human behaviours. Half of adult chimpanzees appeared to associate actions that were much further along the sequence than expected if actions were simply being linked together one-by-one. This provides further evidence that chimpanzees plan action sequences, and then adjust their performance on the fly.
Understanding how these relationships emerge during action organization will be the next key goal of this research, but these could involve behaviours such as chimpanzees pausing sequences to readjust tools before continuing, or bringing several nuts over to stone tools that are then cracked in one long sequence. This would be further evidence of human-like technical flexibility.
Additionally, the results suggest that the majority of chimpanzees organise actions similarly to humans, through the production of repeatable 'chunks'. However, this result did not hold for every chimpanzee, and this variation between individuals may suggest that these strategies for organising behaviours may not be universal in the way they are for humans.
Lead researcher Dr Elliot Howard-Spink (formerly Department of Biology, University of Oxford, now Max Planck Institute of Animal Behavior) said: “The ability to flexibly organise individual actions into tool use sequences has likely been key to humans’ global success. Our results suggest that the fundamental aspects of human sequential behaviours may have evolved prior to the last common ancestor of humans and chimpanzees, and then may have been further elaborated on during subsequent hominin evolution.”
Co-senior researcher Professor Thibaud Gruber (University of Geneva) said: “There has been a renewed interest in the co-evolution of language and stone tool use in human evolution, and our study contributes to this debate. While the connection between our results and early hominin stone tool use can be made more readily, how this connects with the evolution of other complex behaviours, like language, remains an exciting avenue of future research.”
Co-senior researcher Professor Dora Biro (University of Rochester) said: “There is increasing recognition that preserving cultural behaviours in wild animals – such as stone-tool use in West-African chimpanzees – should be incorporated into conservation efforts. Wild chimpanzees and their cultures are critically endangered, yet our work highlights how much we can yet learn from our closest relative about our own evolutionary history.”
As many great apes perform dextrous and technical foraging behaviours, it is likely that the capacity for these complex sequences is shared across ape species. More research is needed to validate this theory, and is a key goal for the team moving forward.
The researchers also plan to investigate how actions are grouped into higher-order chunks by chimpanzees during tool-use. This research will aim to clarify the rules that chimpanzees follow when generating their tool use behaviours. They will also investigate how these structures emerge during development and are shaped across adult lives.
Notes to editors
Interviews with Elliot Howard-Spink are available on request: espink@ab.mpg.de or elliot.howardspink@outlook.com
The paper ‘Nonadjacent dependencies and sequential structure of chimpanzee action during a natural tool-use task’ will be published in PeerJ. It will be available online when the embargo lifts at: https://peerj.com/articles/18484/
For enquiries about advanced view of the paper under embargo, contact: Elliot Howard-Spink: espink@ab.mpg.de or elliot.howardspink@outlook.com
Images and videos relating to the study which can be used in articles can be found at https://drive.google.com/drive/folders/1CM3AdN3ODoxBzf_5RcpLQWeJpZQWNjZ9?usp=sharing These are for editorial purposes relating to this press release only and MUST be credited (see captions document in file). They MUST NOT be sold on to third parties.
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Journal
PeerJ
Article Title
Nonadjacent dependencies and sequential structure of chimpanzee action during a natural tool-use task
Article Publication Date
5-Dec-2024
A male individual cracking nuts using stones. Credit: Dora Biro.
A male individual cracking nuts using stones. Credit: Dora Biro.
Chimpanzees use different types of memory to find insects hidden underground
Remembering over the years where the hidden nests of army ants are
image:
A chimpanzee carries a stick to use as a tool to eat army ants. The chimpanzees insert these tools into the ant nests until the insects climb on the tool and then eat them. /
view moreCredit: Still image extracted by Andreu Sánchez-Megías from a camera trap video taken in the Dindefelo community nature reserve.
Chimpanzees are the animals with the most complex memory, apart from humans. They remember where and when ripe fruits are available, and use this information to decide which trees they will visit and even where they will sleep to eat these fruits first thing in the morning. However, the cognitive strategies they use to find foods of animal origin rather than plant origin are not yet well understood.
Now, experts from the University of Barcelona and the Jane Goodall Institute Spain have led a study that describes the previously unknown cognitive skills deployed by wild chimpanzees in Africa to eat army ants that hide in hard-to-locate underground nests. This is the first paper to describe how these primates make use of spatial and episodic-like memory to extract social insects from nests hidden underground.
The study reveals for the first time how chimpanzees can successfully meet a cognitive challenge to exploit an animal food source in the wild for years.
The findings, published in the journal Communications Biology, expand our understanding of the cognitive strategies of non-human primates, and provide new insights for reconstructing the evolution of cognitive abilities in our lineage.
The study is led by the experts Andreu Sánchez-Megías and R. Adriana Hernandez-Aguilar, from the UB’s Faculty of Psychology and the Jane Goodall Institute Spain. Other participants are Laia Dotras, from the same faculty and institute; Jordi Galbany, also from the same faculty and institute, and the UB Institute of Neurosciences (UBneuro); Adrián Arroyo, from the Seminar on Prehistoric Studies and Research (SERP), the UB Institute of Archaeology (IAUB) and the Catalan Institute of Human Palaeoecology and Social Evolution (IPHES-CERCA). Carlota F. Galán, Nadia Mirghani, Manuel Llana and Justinn Renelies-Hamilton from the Jane Goodall Institute Spain also participated in the study.
Remembering over the years where the hidden nests of army ants are
Army ants (Dorylus spp.), also known as the fearsome marabunta, form the largest colonies of social insects on the planet. These hymenopterous insects are rich in protein and minerals — key nutrients for chimpanzees — but are very difficult to find because they nest under rocks, roots and fallen vegetation and move unpredictably.
As part of the study, the team analysed a total of 679 chimpanzee visits to four army ant nests that occurred from 2018 to 2022 in the Dindefelo community nature reserve, a savannah habitat in the south-east of Senegal.
Andreu Sánchez-Megías, PhD student and first author of the article, explains that “we studied if chimpanzees intentionally return to nests, the strategies they use to detect if ants are present, the availability of these insects and the extent to which chimpanzees consume them”. He notes that the ant nests “are scarce and nearly always impossible to see, and thus, for the chimpanzees, remembering the exact location of the nest is a good foraging strategy. The nests are abandoned and reoccupied at irregular intervals, and this key component of the ants’ behaviour allows chimpanzees to repeatedly visit the same nests to feed on these insects”.
Sight, smell, taste and touch
It seems that these apes remembered previous visits to ant nests and modified their behaviour depending on whether they had encountered the insects on previous visits. The findings indicate that chimpanzees use spatial memory to remember the exact location of hidden ant nests, and episodic-like memory to remember whether they found ants on previous visits to the same nests.
Episodic-like memory is the ability to remember where, when and what happened in past experiences, and is named after episodic memory in humans, which consists of the same abilities plus the ability to verbalize memories. Because non-human animals cannot explicitly communicate to us what they remember, this ability equivalent to human episodic memory is called episodic-like memory.
Furthermore, it is noteworthy that this is the first study to describe how chimpanzees use four senses (sight, smell, taste and touch) to inspect empty nests and detect if there are ants.
Importance for conservation and for understanding human evolution
Serra Hunter professor R. Adriana Hernandez-Aguilar stresses that “it is important to emphasize that the study of chimpanzee cognition in an ecologically relevant context — such as the savannah where our research was carried out — contributes to better understanding the evolution of human cognitive capacities, given that the first hominins inhabited similarly dry, open, and hot landscapes”.
Furthermore, “chimpanzees are an endangered species and learning more about the strategies they use to obtain important foods in the wild helps us to conserve them”, the researchers conclude.
Andreu Sánchez-Megías installing a camera trap in the Dindefelo community nature reserve to record the behaviour of the chimpanzees.
Credit
Photo by Carlota F. Galán-Plana
Chimpanzees use different types of memory to find insects hidden underground (IMAGE)
A female chimpanzee brings her face close to the entrance of an army ant nest hidden under fallen leaves to detect if there are ants inside.
Credit
Still image extracted by Andreu Sánchez-Megías from a camera trap video taken in the Dindefelo community nature reserve.
Journal
Communications Biology
Method of Research
Observational study
Subject of Research
Animals
Article Title
Wild chimpanzees remember and revisit concealed, underground army ant nest locations throughout multiple years
Article Publication Date
5-Dec-2024
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