Human evolution: origin of stone tools (Introduction)

by David Turell , Sunday, March 23, 2025, 17:43 (10 days ago) @ David Turell

Naturally found or hominin made?

https://www.newscientist.com/article/2473159-a-radical-new-idea-for-how-our-ancestors-i...

"When ancient humans first invented stone tools, they may have been trying to emulate naturally formed sharp stones, meaning they would not have needed a huge leap of inspiration.

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"One of the defining features of hominins is their ability to both make and use stone tools, which are useful for butchering animals and opening hard fruits. Creating a stone tool requires hitting two rocks together in precise ways, knocking flakes off one of them in order to shape it into a cutting edge.

"This is called “knapping”, and hominins have been doing it for at least 2.6 million years. There are even older stone tools from Lomekwi in Kenya, dating back 3.3 million years, but these were made using a simpler method: bashing a single stone on the ground.

“'It’s been traditionally thought that the very first stone flakes were produced intentionally or by accident, and then early hominins started to look for things to cut with these new sharp implements,” says Eren. He says this story doesn’t make sense. “For a creature to start to use an item, or to invent an item, there has to be a selective pressure first.”

"Eren and his colleagues argue that hominins found naturally sharp stones, which they used as cutting tools. By doing so, they developed a habit of cutting and began seeking out such stones.

“'Mother Nature is producing knives all over the place,” says Eren. He calls these raw blades “naturaliths”.

"The team has compiled multiple examples of naturaliths. Eren has studied stones from Antarctica, which resemble hominin tools but must have been made by natural processes, since no hominin ever lived in Antarctica. Experiments have also shown that tool-like artefacts can be produced when large animals like elephants and horses trample on stones. Monkeys sometimes accidentally knock flakes off stones. There are also processes that don’t involve living animals, such as waves crashing on rocky shores, frost fracture and glaciers grinding over bedrock.

"If naturaliths were available in hominins’ habitat, says Eren, it would be easy to start using them. “All they need to do is pick them up.”

"For Eren, the appeal of this hypothesis is that it doesn’t require a “eureka moment” of inspiration. “It shortens the cognitive distance between every step in the origin of technology,” he says. He calls it “the most parsimonious proposal” for how hominins invented stone cutting tools.

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“'I think it’s a really intriguing proposal,” says Briana Pobiner at the Smithsonian Institution in Washington DC. “Maybe the invention of stone tools wasn’t this major cognitive leap,” she says, but instead a “natural extension of what hominins were already doing”. She also says that the biggest challenge will be testing the idea, in particular figuring out whether an apparent tool was made by a hominin, an animal or a non-biological process.

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"...in a 1994 study Gregory Westergaard and Stephen Suomi reported that captive capuchin monkeys used stones as cutting tools and modified the stones by striking them against hard surfaces. If capuchins could make and use stone tools, presumably hominins could too. In a series of studies published in 2022, Tennie’s team showed that orangutans could make and use stone tools without training; that wild gorillas sometimes bash stone-like objects together, a prerequisite for knapping; and that humans can figure out basic knapping without help.

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“'Even if hominins were clever enough to spontaneously invent stone tools at will, that does not negate our hypothesis that Mother Nature helped them along,” he says."

Comment: we have a tendency to assume our ancestors were dumb. They may well have invented knapping stone tools after seeing examples in nature or directly invented the process. Now we have both proposals. Animal use of stone tools support the idea that naturaliths were the first step.