New research suggests that a population of Capuchin monkeys in Brazil has been using stone tools for longer than expected. Better yet, they have adapted their tools over generations.
The fact that some primates use stone tools for their daily operations is not new. Chimpanzees in Ivory Coast, for example, have been using these tools for more than 4,000 years. This new discovery is therefore not the oldest known proof of the use of tools by animals. On the other hand, this study teaches us something new: these populations of Capuchin monkeys, installed in a valley of Serra da Capivara National Park, Brazil, seem to have adapted their tools over the generations in order to respond to their environment .
In the Serra da Capivara National Park, the Capuchin monkeys today use stone tools to crack nuts, mainly. The idea of this study, initially, was to determine how long these primates have been using this technique. By unearthing dozens of stones – some of which were buried almost 80 centimeters deep — the British researchers at the University College of London discovered two things.
The first is that the deepest stones were buried in layers of 3,000 year old sediments. Which represents about 450 generations. This gives us a rough idea of the beginning of the “Stone Age” in this population of Capuchin monkeys.
But they also noticed something else: that the tools had evolved over time. The researchers found that from 3,000 to 2,400 years ago, the monkeys used small light stones. At the time, the primates did not seem to be interested in cashews. The “targets” had to be smaller at the time. From 2,400 to 640 years ago, it seems that the use of tools had been stopped. No stone found dates from this time. It is hard to say if the practice was lost and then reinvented later, or if it has continued elsewhere.
Still, from 640 to 565 years old, the tools came back, still as small as at the beginning. They then “disappeared” again until 257 years ago. After that date, the monkeys started using tools again, but this time they were much bigger than the ones used today. A change of practice that again shows a change of regime. It was only a century ago that the Capuchins of this region began to use rocks specially prepared to pound hard cashew shells.
In addition to using tools, which in itself is a cognitive exploit, this species of primate has its own archaeological record. It is difficult to know, however, whether these Capuchin monkeys have developed their technique themselves, or whether they have “copied” the human techniques already in place thousands of years ago.