A key behavior of human evolution observed in gorillas – Sciences et Avenir

Gorille fouillant le sol

It’s a gesture that involves hitting two stones against each other without producing a splinter: this key behavior of human cognitive evolution has been observed in western gorillas according to a study published in Nature. “Vap” and “percussion” with bare hands Our ancestors went through several stages before they could produce stone tools. “Barehand strike” is considered a prerequisite for “barehand percussion”. The latter makes it possible to produce sharp fragments from a stone core. The resulting early artifacts would have played a pivotal role in human evolution. The researchers closely followed the daily lives of two groups of gorillas, or 23 individuals, in the Republic of Congo. They were particularly interested in their eating habits, which they filmed. In almost 300 minutes of recording, only five episodes of “bare-hand attack” were recorded on two gorillas. In the middle of a meal, the two young monkeys did not use stones, but pieces of termites that collided with each other. When feeding on termites, gorillas usually use two techniques. They can directly lick the surface of the pieces of termites they shed or crush them (this is the “piping” technique). Why is this technique different from the “bare hand strike”? “Battering” consists of hammering a piece of thermite held with one hand and the other empty. The two young western gorillas showed wit, holding a piece of termite in each hand. “Adults are much more conformist,” smiles Shelly Masi, researcher at the National Museum of Natural History. “Their intention was probably not to create sharp tools, but to dig up more termites, he explains to Sciences et Avenir. What is important is that they had a goal in mind, and they voluntarily took a new action to achieve it.” Researchers do not expect tools per se. It is not the first time that this behavior has been observed in nature. Japanese macaques (Macaca fuscata), much more distant from our lineage than gorillas, had already made this gesture. For scientists, modern primates offer an opportunity to better understand the factors necessary for the emergence of stone tool production. The next stage of this production, “bare hand percussion”, however, involves additional qualities such as strength and precision. Therefore, it could represent an important turning point in the evolution of the human being. Fragments are sometimes accidentally created when monkeys wield rocks. Bearded Sapajous (Sapajus libidinosus) produce them regularly but never use them. In reality, there are few examples of rock handling in untrained primates. Long-tailed macaques (Macaca fascicularis) are an exception. They dig up stones in the shape of an ax to open shells. Gorillas use few tools There are very few examples of tool use among gorillas. Westerners use pseudo-tools like grass and sticks to scare off intruders. Some of them used a stick to measure the depth of a pool before crossing it. In the wild, it is the least object-using species among the great apes. “Being the largest primate, the gorilla doesn’t need tools, it can only use its strength,” says Shelly Masi. Emmanuelle Pouydebat, CNRS research director who participated in this study, explains to Sciences et Avenir: “What is certain is that it is not a cognitive problem because in captivity they solve problems involving tools very well. They can use sticks to retrieve food hidden in tools. mazes.” Why this difference in behavior? It is the “captivity effect” that could be involved according to the researchers. In other words, even if humans do not intervene directly, with learning for example, the fact of not being in natural conditions generates a different attitude on the part of animals. Capuchin capuchins produce and use sharpening stones The brown capuchin (Sapajus apella) is the only primate species that has intentionally made sharp fragments and used them spontaneously, without being taught. According to the study published in the International Journal of Primatology, individuals have used these cut stones to make their way to rewards. Given these monkeys’ lack of instruction or training, the researchers concluded that brown capuchins have the “natural sensory, motor, and cognitive abilities to make and use cut stones.” The study of western gorillas underscores the food motivation of the “strike with bare hands” behavior observed in the two young primates from the Republic of Congo. According to the scientists, this feeding context could have initiated this gesture in the last common ancestors between gorillas and humans.
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