He instinctively uses the hammer to strike and the sharp stones to cut. And that also tells us more about the skills of our extinct distant ancestors.

What happens if you give a great ape a hammer and sharp stones? That was the question posed in a new study published in the journal PLOS ONE, was central. Although orangutans frequently use tools in the wild, stone tools are alien to the animals. And so, in an interesting experiment, researchers decided to surprise the intelligent great apes with the ‘toy’.

Experiment

The researchers tested two male orangutans living in a Norwegian zoo. Neither had seen a hammer or sharp stones before. They then gave each orangutan the tools and a puzzle box, requiring them to cut through a rope or skin to access the treats inside. Remarkably, both orangutans spontaneously hit the walls of their enclosure with the hammer. In addition, one of them used the sharp stone to cut through the skin. A surprising observation. Because this is the first time an untrained orangutan has been observed using a sharp stone as a cutting tool.

Orangutan Loui experiments with the sharp stone. Image: Motes-Rodrigo et al., 2022, PLOS ONE, CC-BY 4.0

According to researcher Alba Motes Rodrigo, the findings are quite surprising. “Especially because orangutans in the wild don’t use rocks as tools,” she tells Scientias.nl† “In addition, chimpanzees were faced with the same challenge, but failed to solve the puzzle. Our study is therefore the first in which an ape has been observed to use a sharp stone as a knife.”

Use stone tools

According to Motes Rodrigo, it is very interesting to study whether great apes understand what they can do with stone tools. “Studies like this allow us to better understand what skills our extinct hominin ancestors may have had,” she explains. In addition, we also gain a better understanding of how our own Stone Age actually began and what behavior served as a springboard for the deliberate manufacture of sharp stones.”

Power

So what can we learn from studying orangutans? “The discoveries suggest that orangutans can recognize and use the provided cutting tool as such,” said Motes Rodrigo. “They possess certain abilities necessary for making and using stone tools. This means that these abilities are more widespread among great apes than we previously thought. It may have been present in the last common ancestor of orangutans and hominids as early as 13 million years ago.”

Orangutan vs bonobo

An interesting question is why the researchers chose to conduct the study on orangutans and not on bonobos, for example; our closest relatives. “For two reasons,” Motes Rodrigo begins. “First, because orangutans, despite being adept at using tools, as mentioned before, they don’t use rocks in the wild. This allowed us to start our experiments with a clean slate: we could examine the learning process of using the stone tools from the outset, excluding previous knowledge of the tasks. Second, orangutans live in trees. This enabled us to investigate whether tree-dwelling humanoids also knew how to use stone tools.”

On purpose

Although the orangutans in the study managed to figure out on their own what to do with the hammer and sharp stones, there is a big difference from our species. They did not combine these skills with the intentional making of tools, something that humans did start trying in the Stone Age. This suggests that having a few individual skills is not enough to take the remaining steps as well.

Still, the findings are very interesting. “Our results have added another piece to the puzzle of the technological origins of our species,” said Motes Rodrigo. “It shows that a species of monkey that doesn’t use stone tools in the wild, and diverged from our lineage 13 million years ago, exhibits spontaneous behaviors that are crucial for making stone tools.” And that is yet another small step in the search for our own human history.