The practice of learning to prepare food by watching others may have roots in our closest living relative – the chimpanzee. Scientists have discovered that chimpanzees learn how to open and prepare fruit by watching their companions. The study suggests that chimpanzees may be capable of rudimentary human-like traditions within food preparation and provides insight into how humans have developed culture.
University of Portsmouth psychologists, Bruce Rawlings and Dr Marina Davila-Ross, study the evolutionary roots of human culture by examining semi-wild chimpanzees. Their recent study looked at whether chimpanzees socially acquire their natural food preparation skills, known as ‘extractive foraging’ (such as opening hard-shelled fruit) from within their communities. Extractive foraging is an essential skill for both chimpanzees and ancient humans, requiring a combination of intelligence and dexterity.
The results, published today in the journal, Animal Cognition, reveal that the primates socially learn extractive foraging from their companions, demonstrating an important component of culture in chimpanzee natural foraging. The question of nonhuman primate culture has been a contentious subject for several decades.
Mr Rawlings said: “Culture is a hallmark of the human species; we far exceed all other animals in the way we learn skills from within our social communities, particularly within the context of food and cuisine. There is still a huge debate about whether humans are the only species capable of cultural traditions, and indeed how and when this capacity evolved.
“But the clear differences in the natural way the three chimpanzee groups opened the fruits is most likely the result of social learning, which helps form certain behaviour in chimpanzees in a similar way to early human cultures.
“As humans we might learn the best way to crack a nut or how to stone a peach from watching someone else and it appears chimpanzees learn how to handle food in similar ways.”
The study also reported that the chimpanzees occasionally cracked open the hard-shelled fruits and then put the fruits aside to open a few other fruits in a similar way. This indicates that fruits are prepared in advance to eat them one after another at a later stage. Planning in advance indicates a form of intelligence, and these findings link with evidence from the wild where chimpanzees prepare their tools for ant fishing well before using them.
The scientists studied distinct social groups of chimpanzees in the Chimfunshi Wildlife Orphanage in Zambia, Africa. The groups were living in close proximity and in the same kind of environment. But the scientists found that the three groups differed in the way they opened the same hard-shelled fruit.
There were six main techniques that the chimpanzees used to open the fruits: banging two fruits together, scraping or peeling it, cracking the fruit on the ground, banging it on trees or roots, a half bite to remove a little of the shell and get the peeling process started and a full bite like biting into an apple. Importantly, three techniques differed across the groups, and two of these were present in some communities but absent in others.
For example, fruit cracking – hitting one fruit against another – was used by two of the chimpanzee groups but was completely absent in the other group. The same was found for a specific biting technique.
The chimpanzee groups also differed in the number of techniques they combined to open the fruits, with one group averaging almost double the number of techniques for each fruit than the other groups.
Dr Davila-Ross said: “The fruits we studied are also eaten by wild chimpanzees all across Africa and they can be opened without the use of any sticks or stones, unlike the nut-cracking techniques that are also be found in wild chimpanzee populations. Since the fruit preparations did not require any additional tools, we find ecological explanations for the differences unlikely. Furthermore, their social and ecological surroundings showed no notable differences.
“Our analysis on a subspecies level indicated that the differences in foraging techniques are unlikely to result from genetic reasons and they were not influenced by humans.
“Much of the previous research has focussed on captive primate groups, especially with tool use or unnatural feeding behaviours. Half of the chimpanzees in the groups were orphans from throughout Africa and were housed based on their arrival date. Our findings provide important insights to how primordial forms of culture may have emerged.
The research was carried out in collaboration with Professor Sarah Boysen from The Ohio State University, who originated the idea for the study. The study is part of an ongoing field project at Chimfunshi Wildlife Orphanage, led by Dr. Marina Davila-Ross, who started the project in 2007. In a previous study, laughter of chimpanzees was compared across the groups, where it was found that the groups differed how they used laughter as a social response.