Archaeologists unearth the oldest non-human stone tools outside of Africa.
Wild capuchin monkeys in Brazil use stone tools to pound open cashew nuts, and according to a new study the journal Current Biology, they have been doing so for at least 700 years.
When the monkeys use stones as hand-held hammers and anvils to strike at hard foods, they leave behind what the researchers describe as “recognisable cashew processing sites” with used stone tools piled up at the base cashew trees or on tree branches.
The researchers applied archaeological techniques to excavate stones buried at depths of up to 0.7 meters below modern sites where capuchin monkeys are known to use stone tools. Older tools were identified through careful assessment of the size and shape of the stones, and the distinctive damage on the stone surface caused by capuchin pounding.
Chemical analysis confirmed that the residues found on some of the stones came from cashew nuts.
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Through carbon dating, the researchers determined that the oldest stone tools at the site were least 600 to 700 years old, establishing capuchin monkey stone hammers and anvils as the oldest non-human tools known outside of Africa.
“Here, we have new evidence that suggests monkeys and other primates out of Africa were also using tools for hundreds, possibly thousands of years,” said study lead author Michael Haslam, from University of Oxford, in a press release.
“This is an exciting, unexplored area of scientific study that may even tell us about the possible influence of monkeys’ tool use on human behaviour,” he explains. “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.”
The oldest excavated tools did not differ substantially from those used by modern capuchins, being similar in terms of weight and material. According to the researchers, this apparent lack of change over hundreds of years suggests monkeys are conservative in their tool use, preferring not to alter their technology over time, unlike the humans inhabiting the same region.
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