Studying how new natural behaviour was passed among individuals in a wild chimpanzee community, researchers have shown that there could be an evolutionary connection between human and chimpanzee "culture".
"This study tells us that chimpanzee culture changes over time, little by little, by building on previous knowledge found within the community," said co-researcher Thibaud Gruber from the University of Neuchâtel in Switzerland.
In this instance of social learning recorded in the wild, the researchers studied the spread of two novel tool-use behaviours among the Sonso chimpanzee community living in Uganda's Budongo forest.
"This is probably how our early ancestors' cultures also changed over time. In this respect, this is a great example of how studying chimpanzee culture can help us model the evolution of human culture," Gruber added.
The researchers investigated the spread of new variations of "leaf-sponges," which are tools dipped in water to drink from, commonly manufactured by the Sonso chimpanzees by folding leaves in their mouth.
Different individuals were observed to develop two novel variants: moss-sponging (a sponge made of moss or a mixture of leaves and moss) and leaf-sponge re-use (using a sponge left behind on a previous visit).
Neither moss-sponging nor leaf-sponge re-use had been previously observed in Sonso in over twenty years of continuous observation.
The analysis began when Nick, a 29-year-old alpha male chimpanzee, made a moss sponge while other chimpanzees watched.
By using a technique called network-based diffusion analysis, the researchers estimated that each time a "naive" chimpanzee observed moss-sponging, this individual was 15 times more likely to develop the behaviour.
This striking effect contrasted with the re-use behaviour in which social learning played much less of a role.
The study indicates that group-specific behavioural variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, before the advent of modern human species.
The study appeared in the journal PLOS Biology.
