A new study suggests that capuchin monkeys might have developed a technological solution to feed for at least 700 years. Capuchins in Brazil use stone tools to crack hard-shelled fruits and seeds to eat.

Scientists from Oxford and the University of São Paulo described on Monday that they found out dozens of stone hammers and anvils in Brazil. The findings, published in the scientific journal Current Biology, show that capuchins in the Serra da Capivara National Park, a park located in the northeastern region of Brazil, have used stone tools to survive in the habitat.

Capuchin monkey. Credit: UCLA

According to researchers, Brazilian capuchins have been using stone tools to crack open cashew nuts for at least 700 years. The archeological evidence exhibits the earliest archaeological examples of monkey tool use outside of Africa’s.

The research, led by Dr. Michael Haslam of the University of Oxford and colleagues from the University of São Paulo explained the findings correspond to the oldest non-human tools to be found outside of Africa, but they also refer to the oldest known tools not belonging to humans or chimpanzees.

“Until now, the only archaeological record of pre-modern, non-human animal tool use comes from a study of three chimpanzee sites in Cote d’Ivoire in Africa, where tools were dated to between 4,300 and 1,300 years old. Here, we have new evidence that suggests monkeys and other primates out of Africa were also using tools for hundreds, possibly thousands of years. This is an exciting, unexplored area of scientific study that may even tell us about the possible influence of monkeys’ tool use on human behavior. For example, cashew nuts are native to this area of Brazil, and it is possible that the first humans to arrive here learned about this unknown food through watching the monkeys and their primate cashew processing industry,” said Haslam.

Researchers observed wild capuchins in their habitat at Serra da Capivara National Park carrying out a recognizable cashew processing method to crack open hard-shelled foods. The groups of new capuchins living at the park used stones as hand-held hammers and anvils to beat hard over hard seeds and cashew nuts.

Capuchins’ feeding mechanism

It seems like Brazilian capuchins created a feeding system they passed through generations. While picking up stone tools for the task, capuchins choose tools based on size and material. For capuchins, it is a matter of selecting particular stone tools which must also be the most suitable cashew-crackers.

Researchers realized capuchins create likewise specific cashew processing sites where they leave stone tools once they use them, such as the base of cashew trees or on tree branches.

Using archeological methods, researchers evaluated a total of 69 stone samples to observe capuchins technology for roughly 2,500 years. They inspected the stone tools to determine how optimal and practical the mechanism was. It was size, shape, damage and dark-colored residues what let scientists determine the species has been cracking open hard-shelled foods all over time.

“If tool use was indeed part of that colonizing process, then we can hypothesize that this behavior may be hundreds of thousands of years old. Of course, the only way to know for sure is to keep digging,” said Haslam.

The whole process is learned from young capuchins, and this is how the species has maintained the feeding mechanism during several generations. Researchers have estimated that around 100 generations of capuchins have used the method to survive in the semi-arid region of northeast Brazil. Haslam and his colleagues discovered older stones that might have been used by more elderly capuchins presented similarities with the tools used by modern capuchins. The findings point out also to the conservatism of the species. In contrast to human beings, capuchins remain faithful to traditions, in this case, the feeding method.

Scientist concluded that it might be a reason to explain how capuchins were able to colonize such a challenging habitat for the species. Brazil’s northeast offer the little variety of food for capuchins, so they were forced to develop a technological solution to feed on the only source they had at their disposal: hard-shelled fruits.

Haslam added that the discovery might be a hint to link the possible influence of monkeys’ tool use on human behavior. It has been widely proved that humans learn behavioral practices from other animals. It is equally possible that humans had acquired capuchins’ crack-cashew system once they shared same environments.

Capuchins usually live in forests, such as the Amazon, where they encounter an entirely different variety of food from the one provided by Brazil’s northeast region.

Source: Science Daily