Stone flakes made by monkeys cast doubt on ancient human ‘tools’

By utilizing stones to interrupt open nuts, monkeys by accident create sharp-edged flakes that appear like the instruments believed to have been utilized by our historic human family members.

The discovering casts doubt on whether or not all of the stone flakes present in archaeological digs actually are the instruments of early hominins — and raises the chance that they may be unintended by-products of hitting issues with complete stones, says Lydia Luncz on the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

In 2016, Luncz and her colleagues realised that Brazilian capuchins produce stone flakes from the rocks they use to pound meals, dig and interact in sexual shows, with out essentially which means to. The flakes have been primarily similar to these present in hominin settlements courting to at the least 3 million years in the past. It made the staff ponder whether the artefacts actually mirrored any technical planning by these early people.

Since then, Luncz and her colleagues have been finding out device use in long-tailed macaques (Macaca fascicularis) on the islands of Phang Nga Bay in Thailand. In the forests there, Luncz stumbled throughout nut-cracking websites – a shock, as long-tailed macaques weren’t beforehand identified to interrupt open nuts.

The staff arrange motion-activated cameras to review the behaviour of the wild macaques. During 100 hours of footage, the staff witnessed monkeys by accident creating flakes as they struck nuts between two stones – serving as a hammerstone and an anvil – after which leaving the damaged stones to search out new, complete stones.

This is sort of precisely what the capuchins did within the earlier research, says Luncz, displaying that the flake-making wasn’t a one-off. “This was occurring on the other side of the planet, in a different ecosystem and a different species,” she says. “So it was just so obvious that this is a primate thing. This is a foraging behaviour that we assume also happened in early hominins.”

So far, capuchins, chimpanzees and long-tailed macaques are the one non-human primates identified to make use of stone instruments within the wild – and all of those are actually confirmed to accidentally produce flakes that appear like historic hominin instruments, she says.

The staff then in contrast 1119 stone flakes from the macaques’ nut-cracking websites with artefacts discovered at hominin websites in Ethiopia, Kenya and Tanzania. The monkeys’ skinny, flat, extensive stone flakes – starting from 1.3 to 7.9 centimetres in size – have been “almost indistinguishable” from flakes that have been related to historic people as much as 3.3 million years in the past, says Tomos Proffitt, one other member of the analysis staff on the Max Planck Institute for Evolutionary Anthropology.

While there have been a couple of totally different traits – the monkeys’ flakes have been, on common, smaller and thicker than the hominin flakes, for instance – they have been nonetheless so comparable that they might have changed as much as 70 per cent of the traditional people’ instruments.

The findings may problem the present understanding of early stone expertise, says Proffitt. “I wouldn’t go so far as to say that all of the old material is not intentional,” he says. “But what our study shows is that we can’t be 100 per cent certain that every single flake in the early Stone Age archaeological record was intentionally made. There may be a component within that record that’s unintentional.”

For Zeray Amelseged on the University of Chicago, the research principally illustrates the gradual development of cognitive evolution in primates. “Is what we find in the archaeological record just a result of process without intentionality?” he says. “I don’t think we have an answer, but an important point in this paper is that the actions of stone tool-making and stone tool use have a much deeper history in time as well as in the primate world. And that’s what’s becoming clearer.”