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A new study looks into the history of stone tools used by wild macaques in coastal Thailand. It finds they have been using them for decades…and possibly thousands of years… to crack open shellfish and nuts.

Rhesus macaque baby monkey inspecting straw Jeannette Katzir Photog

Image:, Rhesus Macaque baby Monkey inspecting straw

While there have been several studies observing living non-human primates, this is the first report into the archaeological evidence of tool use by Old World monkeys. The research, led by the Primate Archaeology Research Group at the University of Oxford, opens up novel research possibilities. The paper, published in the Journal of Human Evolution, says this is just the first step in finding out how their behaviour compares with that of early humans living in similar environments.

From a distance in boats off the coast, researchers spent hundreds of hours watching how groups of macaques in the marine national park on Piak Nam Yai Island selected stones as tools to crush marine snails, nuts and crabs. While the tide was out, the macaques broke open oysters attached to large boulders. They dislodged the top half of the shell using their crushing tool and then scooped out the meat with their fingers from the remaining part still attached to the rock. The researchers also found that once a macaque had a good stone fit for the job, they would keep it to crack open other shells or nuts before dropping it. Once the job was done, the macaques often discarded their tools around the same boulders where they had enjoyed their meal.

Read more on the University website (opens new window)