In the history of mankind, the Stone Age is the period in which we began to make stone tools, something that eventually helped us to evolve a more complex intelligence. Now, a group of scientists have just discovered that same behavior in another non-human primate.
Brendan Barrett, of the Max Planck Institute of Ornithology in Radolfzell, Germany, and his colleagues have discovered in the jungle of Panama, a species of capuchin monkey with a thin body and no tufts that uses stone tools. The results of the study have been published on the BioRxiv press site.
According to Barrett, this feature has only been found in a specific group since nearby populations do not use stone tools. The finding might suggest that primates, perhaps even our ancestors, happen to run into the Stone Age by chance. Other primate species have also been observed using stone tools to access food, including chimpanzees in West Africa, macaques in Thailand and several species of capuchin monkeys living in South America.
It is estimated that the tufted and non-tufted hoods separated from each other about 6.2 million years ago, says Barrett. “This is a time of similar divergence between our lineage and the last common ancestor of chimpanzees and bonobos,” he says. In other words, non-tufted capuchins are the fourth distinct type of non-human primate that is known to use stone tools regularly.
It only happens on an island
Although Barrett is the one who is publishing the study, he has not been the first to observe this behavior in white-faced capuchins. The independent researcher Alicia Ibáñez, noticed it in the Coiba National Park of Panama.
Then, in March of 2017, Barrett and his co-workers followed up the observation, placing cameramen in three maritime islands of the park. They discovered that the male capuchins of the island of Jicarón used stone tools to break open coconuts, crabs and snails. The Capuchins in other parts of Jicarón did not use stone tools, nor did the Capuchins in the other islands.
The scientist believes that several factors could have encouraged the Jicarón capuchins to experiment with stone tools. There are no land predators on the island, so monkeys can afford to spend more time on the ground with their attention focused on the use of tools. There are also few easily accessible food sources on the island, which makes it worthwhile for cappuccinos to use stones to break nuts and tough shells.
However, this scenario leaves a mystery. Capuchins in other parts of the island and in the others also experience these conditions, but they do not seem to use stone tools. “We were surprised that this behavior seems geographically localized,” says Barrett. Faced with that, Michael Haslam at the University of Oxford believes that there can be a simple explanation. “There must be a strong element of opportunity, perhaps more important, in the adoption of stone tools in primates,” says New Scientist.
Maybe you need a single hyperintelligent person to jump and start using stone tools, while others copy the idea. “Good innovations are pretty rare, but if they’re adaptive they can take off,” says Barrett.
But that still does not explain why other Capuchins living in Jicarón do not use stone tools, he says, because individuals often migrate between groups and useful innovations should be extended. He hopes that a more detailed study of the monkeys in the coming years will help solve that puzzle.
This would not be the first time that the capuchins call the attention of science for the use of tools, an investigation last year even went so far as to say that this small species could have taught the use of tools to humans themselves.