Orangutans, great apes found in Borneo and Sumatra, are known for their largely arboreal existence. Their intelligence is well-documented, encompassing problem-solving, memory, and communication through gestures and mime. While their capacity for tool use has been observed, their abilities with stone tools were less understood until recently. This new understanding challenges previous assumptions about their cognitive capabilities.
Discovering Orangutan Tool Use
The discovery of orangutans engaging in stone tool use marks a significant scientific advancement. Early observations of tool use in wild orangutans were limited, often involving sticks for scratching or simple shelters. More recent research, however, has revealed a more sophisticated range of behaviors. At the Suaq Balimbing research site in Sumatra, scientists documented orangutans using tools to extract honey, ants, or termites from tree cavities. This area has been a focus of long-term studies, providing detailed behavioral and environmental data since the 1990s.
Further investigations involved captive orangutans to explore their abilities. At Kristiansand Zoo in Norway, two male orangutans, untrained and unexposed to stone tools, were given concrete hammers and prepared stone cores. While they spontaneously hit hammers against surfaces, they did not initially direct strikes at the stone cores to produce flakes. A subsequent experiment showed that when provided with a human-made sharp flint flake, one orangutan spontaneously used it to cut through a silicon skin to access a food reward. This demonstrated an aptitude for recognizing and utilizing sharp edges.
How Orangutans Use Stone Tools
Orangutans demonstrate specific actions when utilizing stone tools, particularly in controlled experimental settings. In studies, researchers observed them using concrete hammers to strike against surfaces, an action known as lithic percussion. While initially not directed at producing sharp flakes, this behavior shows a foundational skill related to stone tool creation.
When presented with sharp stone flakes, orangutans used them for cutting. One orangutan successfully used a human-made flint flake to cut through a silicon skin covering a puzzle box to obtain a food reward. This indicates their ability to recognize sharp stones as functional cutting implements. These observations, while primarily in controlled environments, suggest a latent capacity for stone tool manipulation that may not be extensively observed in their natural, largely arboreal habitat where stones are less available.
The Significance of Orangutan Stone Age
The revelation of orangutans’ stone tool capabilities holds implications for understanding primate cognition and the evolution of tool use. This discovery suggests that the fundamental prerequisites for early stone tool technologies, such as striking with stone hammers and recognizing sharp edges for cutting, may have existed in the last common ancestor shared by orangutans and humans, potentially as far back as 13 million years ago.
Comparing orangutan tool use to that of other great apes, like chimpanzees and bonobos, highlights commonalities and unique aspects. While chimpanzees are known for their diverse tool use, including stone tools for cracking nuts, the spontaneous recognition and use of sharp stones for cutting by untrained orangutans is a novel finding. This challenges previous assumptions that such skills might be restricted to certain ape lineages. The capacity for cultural transmission of learned behaviors is also relevant, with evidence suggesting orangutans exhibit culturally based behaviors dating back 14 million years. This implies that complex tool use, once developed, could be passed down through generations, influencing human evolutionary history.