New research, just published in the journal Current Biology, shows that capuchin monkeys in Brazil have been using stone tools for at least 700 years. This represents the earliest known case of monkey tool use outside of Africa. The authors speculate that early humans in Brazil may have learned from watching the monkeys.
Brazilian bearded capuchin monkeys (Sapajus libidinosus) use basic stone tools to crack open cashew nuts, a favorite food. They use large, heavy stones as anvils and smaller stones as hammers. These tools are left in what the researchers call “’recognizable cashew processing sites”, spots that the capuchins return to when they need to break open nuts and seeds. The skill gets passed on through the generations, with older monkeys teaching the younger ones.
The research team dug 0.7 meters at one of the processing sites, excavating 69 stones. The researchers identified which rocks were tools based on shape, size, and the type of wear. They also used mass spectrometry to look for cashew nut residue. The researchers then dated the tools using carbon dating methods. They found that the oldest tools were 600 to 700 years old. The oldest tools closely resembled modern capuchin tools, showing that the monkeys didn’t change their methods over time.
These findings suggest that the capuchins were using stone tools before humans first arrived in Brazil. The authors believe that early humans may have learned to crack open local nuts and seeds by watching the monkeys. The paper also points out that the capuchins are conservative about their tool use. The tools didn’t change over time, showing that the monkeys had no interest in changing or improving their tools. This is in contrast to humans, who are known for constantly updating their technology. The study provides insight into the evolution of primate technology, including the idea that monkey tool use may have influenced human behavior.
Michael Haslam et al. Pre-Columbian monkey tools. Current Biology (2016).