A new study has found that chimpanzees are able to organise behaviours in complex action sequences and suggests the fundamental abilities underlying human language and technological culture may have evolved before humans and apes diverged millions of years ago.
“As humans, we perform many complex behaviours that involve complicated sequences – things like organising words into sentences or organising actions into highly technical processes of tool manufacturing and use,” explains lead researcher Dr Elliot Howard-Spink, formerly at the University of Oxford’s Department of Biology, now at the Max Planck Institute of Animal Behaviour.
"Understanding how these capacities evolved is challenging because we can only use artefacts of other hominin species that evolved before our own - we can’t see their behaviours. By studying the behaviors of other apes, such as chimpanzees, we can try to identify any shared capacities between us and them, which perhaps evolved before the last common ancestors of humans and chimps.”
Organised sequences
Complex action sequences by humans rely on the ability to organise behaviours by hierarchical 'chunks’ and to understand relationships between separate elements of a sequence.
"For humans, this ‘chunking’ allows us to organise actions into flexible sequences,” says Howard-Spink. "For example, if you’re making a cup of tea and the teabag’s already been placed in the cup by a friend, you can leave out the chunk of actions required to get yourself a mug and teabag. Also, if something goes wrong in a sequence, such as the mug falls over, you can add in actions to rectify the situation, such as cleaning up the tea and adding more water.”
It was unknown whether the ability to flexibly organise behaviours in a sequence in this way is unique to humans or is also present in other primates.
- Intimate photos show chimps using insects as medicine to treat each other's wounds in Gabon
- Chimp moms play 'airplanes' with their kids, even when they're tired and hungry
- Menopause observed in chimpanzees
In the new study, researchers investigated the actions of wild chimps, humanity’s closest relatives, whilst using tools, looking at whether their actions appeared to be organised into sequences, rather than 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 database of video footage of wild chimps in the Bossou forest in Guinea, where chimps were recorded cracking hard-shelled nuts using a hammer and anvil stones – one of the most complex, naturally-occurring, tool-use behaviours by animals in the wild ever documented.
Using cutting edge statistical models, the researchers found that half of the adult chimps appeared to associate actions that were much further along the sequence than expected, which provides evidence that chimps plan action sequences and can flexibly adjust their behaviour as needed.
"The sequences of actions wild chimpanzees use to perform their tool-use behaviours share many properties with those of humans,” says Howard-Spink. “For example, we found evidence that chimpanzees organise their actions into ‘chunks’ of behaviour, much like humans do, and that chimpanzees understand relationships between actions that are separated in behavioral sequences.
"Other studies have previously shown how chimpanzees must carry tools over distances in the forest, or they can leave out steps from tool-use behaviours that are not required. But finding objective, systematic evidence for these 'chunks’ and ‘long-distance’ relationships between elements has been challenging. This is the gap that we fill.”
Some chimps have been observed, for example, pausing to reorient tools or to replace nuts on anvils when they roll off, or checking if nuts are cracked and trying to peel them before returning to striking them.
What's next?
The researchers now want to investigate all the ways these hierarchical chunks are formed and how chimp cognition leads to ‘chunking’.
Many great apes perform dextrous and technical foraging behaviours, which means it’s likely the capacity for complex action sequences is shared across other ape species. Researchers also plan to look into this theory.
Does all this mean chimps might evolve even more intelligent and sophisticated behaviours, and that we’re on the way to a Planet of the Apes scenario?
“What will happen next in evolution for chimpanzees is not clear,” says Howard-Spink. "Evolution doesn’t plan far ahead - it makes decisions about what is useful right now. Archeological evidence from other studies of chimpanzees’ stone tools suggest these behaviours have already been around for thousands of years, likely in the state they’re currently in. So unlike human cultural behaviours, the tool-use behaviours of chimpanzees seem to change very slowly.
"Further research is needed to understand why humans can produce new technologies at such fast rates. In all likelihood, it will be due to a lot of different factors.”
Main image: Adult female cracking nuts using stone tools. She is being observed by an infant female (1 year old)/Tetsuro Matsuzawa
More wildlife stories from around the world
- Robots just collected something significant from the breath of these rare orcas
- An immense creature is moving through the vast swamps of the Everglades National Park
- Orcas are now hunting whale sharks – and they're doing it in an astonishing way
- A long-lost sound has returned to the great mountains of Yosemite National Park