Chimpanzees show each other objects just for the sake of it, researchers have found, revealing that it is not only humans who like to draw attention to items that have captured their interest.
As anyone who has spent time with a child knows, even very young humans like to point out objects to others. However, it was previously thought that this behavior only occurs in our species.
Now researchers say they have found an instance of a chimpanzee showing her mother a leaf.
“She’s not offering it for food. She doesn’t want her mum to do anything. She just wants them to look at it together, and be like ‘Oh, cool, nice!’,” said Prof. Katie Slocombe of the University of York, a co-author of the study.
Writing in the Proceedings of the National Academy of Sciences, Slocombe and colleagues noted that even close relatives of humans, such as great apes, were thought only to gesture to objects for particular purposes.
“Sometimes when they’re grooming in this community of chimpanzees, they’ll scratch a particular location on their body … and that indicates ‘I want you to groom me here’,” said Slocombe. “If they have their hands out towards something, it means ‘give me that’.”
It was while studying the Ngogo chimpanzee community in the Kibale national park, Uganda, that Slocombe and colleagues captured video of footage of an adult female, called Fiona, grooming a leaf – a common behavior in which chimpanzees pluck foliage, peer at it, and stroke it.
But then Fiona did something unusual: she held the leaf out to her mother, Sutherland, who was sitting next to her. When Sutherland only lowered her eyes, Fiona thrusted the leaf further forwards – possibly, the team suggested, because she did not see her mother’s response.
“She does kind of three separate movements, each time kind of putting it closer and closer to her mother’s face,” said Slocombe.
Once Sutherland moved both her eyes and head towards the foliage, Fiona withdrew the leaf, and continued grooming it.
To explore possible explanations, the researchers examined 84 video clips of chimpanzees in the Ngogo and Kanyawara communities that were grooming leaves near at least one other individual.
While a leaf was often watched simultaneously by the chimpanzee grooming it and an onlooker, they were not recorded eating the foliage.
Only five of 58 clips capturing a chimpanzee’s behavior both before and after leaf-grooming showed them subsequently grooming another chimpanzee or playing with them.
The upshot, said the team, is that Fiona was likely to have been neither offering food nor seeking another activity. Instead, she probably just wanted to show her mother the leaf.
Prof Frans de Waal, a primatologist at Emory University who was not involved in the work, described the observation as remarkable.
“It is not the first time that we have seen a suggestion that chimpanzees voluntarily point out information to others – I myself have described such incidents – or that they may teach others new information, but this is now the best documented case,” he said .
“It signifies that chimpanzees, and perhaps also other apes, grasp that other individuals gather information the way they do themselves, and are willing to share information with others without any prompting or rewards or self-serving purposes.”
While Slocombe acknowledges the team has recorded just one instance of the behavior, she hopes experts may now look for similar examples, or even find them in previously collected footage. But, she said, questions remain.
“Probably our last common ancestor with chimpanzees might have done this occasionally, like chimpanzees do now,” she said. “So what we then need to understand is what was the selection pressure to increase our motivation to do this more.”