Stone flakes made by monkeys cast doubt on ancient human 'tools'

By utilizing stones to interruption unfastened nuts, monkeys accidentally make sharp-edged flakes that look similar the tools believed to person been utilized by our past quality relatives.

The uncovering casts uncertainty connected whether each the chromatic flakes recovered successful archaeological digs truly are the tools of aboriginal hominins — and raises the anticipation that they mightiness beryllium accidental by-products of hitting things with full stones, says Lydia Luncz astatine the Max Planck Institute for Evolutionary Anthropology successful Leipzig, Germany.

In 2016, Luncz and her colleagues realised that Brazilian capuchins nutrient chromatic flakes from the rocks they usage to lb food, excavation and prosecute successful intersexual displays, without needfully meaning to. The flakes were fundamentally identical to those recovered successful hominin settlements dating to astatine slightest 3 cardinal years ago. It made the squad wonderment whether the artefacts truly reflected immoderate method readying by those aboriginal humans.

Since then, Luncz and her colleagues person been studying instrumentality usage successful long-tailed macaques (Macaca fascicularis) connected the islands of Phang Nga Bay successful Thailand. In the forests there, Luncz stumbled crossed nut-cracking sites – a surprise, arsenic long-tailed macaques weren’t antecedently known to interruption unfastened nuts.

The squad acceptable up motion-activated cameras to survey the behaviour of the chaotic macaques. During 100 hours of footage, the squad witnessed monkeys accidentally creating flakes arsenic they struck nuts betwixt 2 stones – serving arsenic a hammerstone and an anvil – and past leaving the breached stones to find new, full stones.

This is astir precisely what the capuchins did successful the earlier study, says Luncz, showing that the flake-making wasn’t a one-off. “This was occurring connected the different broadside of the planet, successful a antithetic ecosystem and a antithetic species,” she says. “So it was conscionable truthful evident that this is simply a primate thing. This is simply a foraging behaviour that we presume besides happened successful aboriginal hominins.”

So far, capuchins, chimpanzees and long-tailed macaques are the lone non-human primates known to usage chromatic tools successful the chaotic – and each of these are present proven to incidentally nutrient flakes that look similar past hominin tools, she says.

The squad past compared 1119 chromatic flakes from the macaques’ nut-cracking sites with artefacts recovered astatine hominin sites successful Ethiopia, Kenya and Tanzania. The monkeys’ thin, flat, wide chromatic flakes – ranging from 1.3 to 7.9 centimetres successful magnitude – were “almost indistinguishable” from flakes that were associated with past humans up to 3.3 cardinal years ago, says Tomos Proffitt, different subordinate of the probe squad astatine the Max Planck Institute for Evolutionary Anthropology.

While determination were a fewer antithetic trends – the monkeys’ flakes were, connected average, smaller and thicker than the hominin flakes, for illustration – they were nevertheless truthful akin that they could person replaced up to 70 per cent of the past humans’ tools.

The findings could situation the existent knowing of aboriginal chromatic technology, says Proffitt. “I wouldn’t spell truthful acold arsenic to accidental that each of the aged worldly is not intentional,” helium says. “But what our survey shows is that we can’t beryllium 100 per cent definite that each azygous flake successful the aboriginal Stone Age archaeological grounds was intentionally made. There whitethorn beryllium a constituent wrong that grounds that’s unintentional.”

For Zeray Amelseged astatine the University of Chicago, the survey mostly illustrates the gradual progression of cognitive improvement successful primates. “Is what we find successful the archaeological grounds conscionable a effect of process without intentionality?” helium says. “I don’t deliberation we person an answer, but an important constituent successful this insubstantial is that the actions of chromatic tool-making and chromatic instrumentality usage person a overmuch deeper past successful clip arsenic good arsenic successful the primate world. And that’s what’s becoming clearer.”

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