Tools are some of the best evidence for the existence of early human species which follow their evolution to the modern humans of today. Now, a group of researchers reports to have found evidence of capuchin monkeys using tools also, which could shed light on the process of their evolution.
A group of researchers working with different institutions in Brazil and the UK discovered stone tools that were likely used about 3,000 years ago by capuchin monkeys. Their findings were published in the journal Nature Ecology and Evolution. The paper details how they used the stone tools, and the archaeological processes that were necessary to find the stone tool artifacts.
Previous studies showed that chimpanzees used different tools that helped them survive, with evidence being traced back 4,000 years. That said, evidence of capuchin monkeys using tools is not that surprising. There is also evidence that suggests birds used twigs to retrieve food. Researchers are continuing to conduct studies that focus on non-human eating using different tools, although this act as a whole, not much is known about through evolutionary history.
The new study surveys capuchin monkeys that live in Brazil’s Serra da Capivara National Park, and how they utilize those tools. The monkeys were supporting themselves by using quartz stones which helped them open cashew nuts. The study describes that the monkeys would place the nuts on a larger stone (also known as an anvil), or a harder tree root and then smash it with a quartz rock. That process, according to the researchers, leaves marks and signs on both the used rock as the tool and the anvil that is used. Scientists noticed that the repetitive bashing would leave brown stains on the anvil or tree, given that the cashew shells are brown.
Seeing this behavior encouraged the researchers to excavate earlier archaeological evidence of this behavior in the same areas, as they wanted to find stone artifacts with the same bashing marks. The researchers found that there are artifacts of capuchin monkeys using tools nearly as far back as 3,000 years ago.
The deeper they dug, the more evidence of this behavior scientists found, providing evidence of older rock tools that capuchin monkeys used. The researchers also found that over the years, the monkeys also changed the size of the tools they used. That said, the oldest artifacts were small, and showed a lot of damage, which suggests that those animals missed their targets a lot. The newer rocks that date 560 years back, appear to be larger, but only for a couple of hundred years. Again, 300 years ago, capuchin monkeys started using rocks similar to the ones they use today.
The researchers need to do further research to support their theory, as they only assume that it was capuchin monkeys using those tools, with no evidence to prove them otherwise. Also, it’s likely that the diet of capuchin monkeys changed over time, and they needed suitable tools that would enable them to smash the food they wanted to consume.