It turns out that like our ancestors, monkeys also used stone tools to make their lives more convenient. A research team from the University of Oxford and the University of São Paulo in Brazil found the first evidence that Brazilian capuchins have been using tools made of stone to open cashew nuts for 700 years.
As stated by the study published in Current Biology, the capuchins at the Serra da Capivara National Park in northeast Brazil use smooth, hard quartzite stones as hammers and flat sandstones as anvils to crack open hard food like cashew nuts and seeds. The young monkeys learn this practice from older ones.
To determine how this behavior changed over time, the research team gathered 69 stones from cashew processing sites, which are usually the base of cashew trees or tree branches where the monkey leave the stones after using them. Using a technique called mass spectrometry, the team found that the dark-colored residues on the tools came from cashew nuts. Carbon dating reveals that these were between 600 and 700 years old.
These stone tools were used even before the arrival of Europeans to the New World and are the earliest archaeological examples of monkey tool use outside of Africa, where other research teams found that chimpanzees also used tools dating back 4,300 and 1,300 years. The researchers believe that 100 generations of capuchins have been using tools. Interestingly, despite this long period, the tools the monkey use today are still the same material and weight used by the monkeys hundreds of years ago, suggesting that the capuchins do not like change.
The study prompts further research into the origins and spread of tool use among monkeys from the New World. The researchers add that their findings could open up new discussions about the theory that humans actually got their idea of using stone tools from monkeys.