The Stone Age might conjure up images of early humans, sitting around a campfire or hunting prehistoric beasts, but evidence shows that we’re not the only species that has learned how to work with stone tools.
Wild chimpanzees (Pan troglodytes) use stone tools to crack open nuts. They place the nut on a flattened rock (known as an anvil) and strike it with a second stone (known as a hammer). Thick branches can also be used.
Evidence from Côte d’Ivoire in Africa shows that chimpanzees have been using this technique for more than 4,000 years. This suggests that stone tool use might be a trait that both humans and chimpanzees inherited from their last common ancestor. Although, it’s also possible that both species learned this skill independently of each other.
The hammer-anvil technique is also used by several species of primate, including capuchins (Sapajus libidinosus) in Brazil and long-tailed macaques (Macaca fascicularis) in Thailand. In the case of capuchins, the stone hammers can weigh up to 1kg (2.2lbs) – one-quarter of their body weight – and it can take them up to eight years to master the skill. Archaeological evidence shows that capuchins have been using nut-cracking stones for at least 3,000 years.
It’s not just primates that use stone tools though. Otters use stones to crack open shellfish and pry sea snails from rocks, and New Caledonian crows drop hard nuts onto ‘anvil’ rocks from a great height to break them open.
Using stone tools was once thought to be unique to Homo sapiens, but archaeologists have discovered stone artefacts from earlier hominin species, such as Homo habilis.
Nevertheless, manufacturing stone tools remains a cornerstone of human evolution, and archaeologists have used stone-tool artefacts to piece together the behaviour and movements of ancient humans. So the discovery that other primates also use stone tools has called some of the oldest archaeological sites into question.
In 2022, archaeologists in Argentina concluded that 50,000-year-old stone tools in Brazil may have been created by capuchin monkeys, not humans. The quartz tools look remarkably similar to tools crafted by present-day capuchins.
If these ancient tools were indeed left behind by monkeys, it would extend the record of their stone-tool use by thousands of years and cast doubt on the timing of Homo sapiens’ arrival in South America.
Archaeologists have also highlighted striking similarities between stone tools crafted by early humans and shards of stone created by mistake when long-tailed macaques using the hammer-anvil technique miss and accidentally hit the two stones together.
The monkeys seemingly have no use for these sharp-edged shards. But the discovery highlights a plausible chain of events that our ancestors might have followed three million years ago. Perhaps early humans were inspired to create their own cutting tools after accidentally creating shards in a similar way.
The similarity between the monkeys’ accidental shards and humans’ deliberate cutting tools makes interpreting archaeological remains more challenging and reopens the debate over the origins of some of the world’s oldest stone-tool artefacts.
This article is an answer to the question (asked by Juanita Andrade, via email) 'Are we the only species to have been through a stone age?'
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