3-million-year-old stone tools found, and our ancestors likely didn’t make them

Evidence suggests the tools were used by the human relative Paranthropus, which scientists previously believed relied only on its teeth and jaws to eat.

By Tom Metcalfe
Published 10 Feb 2023, 16:45 GMT
Scientists have unearthed more than 300 stone tools at the Nyayanga site in southwestern Kenya (pictured in 2014, prior to excavation).
Photograph by T.W. Plummer, Homa Peninsula Paleoanthropology Project

Archaeologists have discovered distinctive stone tools at a site in southwestern Kenya that may be up to three million years old, making them the oldest of their kind.

Even more surprising, the tools were found alongside fossils from the hominin Paranthropus, which is not an ancestor of modern humans.

The discoveries reinforce theories that hominins outside our own Homo genus also used stone tools. They also push back the earliest date for Oldowan technology—a tradition of toolmaking in eastern Africa dating to the early Palaeolithic—by hundreds of thousands of years.

Palaeoanthropologist Emma Finestone, assistant curator of human origins at the Cleveland Museum of Natural History in Ohio, says it was suggested years ago that Paranthropus might have been a tool user.

But the idea had fallen out of favour, she says, in part because Homo hominins—who definitely used stone tools—were thought to be smarter, and because Paranthropus had large teeth and jaws, which meant they may not have required tools to process food. 

But with this new find, “now I’m changing my mind,” says Finestone, who was part of the team that worked from 2014 until 2022 at Nyayanga, an archaeological site in southwestern Kenya on the shores of Lake Victoria.

Scientists discovered two molars of Paranthropus, a hominin that is not a direct human relative.
Photograph by S. E. Bailey, Homa Peninsula Paleoanthropology Project
Example of an Oldowan percussive tool found at the Nyayanga site in 2016.
Photograph by T.W. Plummer, J.S. Oliver, and E. M. Finestone, Homa Peninsula Paleoanthropology Project

A large natural amphitheatre there is filled with stone tools—mostly made from rocks such as quartz and rhyolite—and the fossilised bones of animals eaten by early hominins. The tools include sharp pieces for chopping and scraping; the stone cores, or source material, they were flaked from; and the hammerstones used to strike the cores.

Technological breakthrough

The research team, led by Thomas Plummer, has identified more than 300 Oldowan tools at the site over almost 10 years; in 2019 they also discovered a Paranthropus tooth. A second tooth from a different Paranthropus individual has since been unearthed amid a fossilised “scatter” of butchered hippopotamus bones.

While most people had thought Paranthropus relied only on its stout teeth and jaws to eat, “here you’ve got Paranthropus at a site with stone tools and a butchered hippo,” says Plummer, a professor of anthropology at Queens College of the City University of New York and the lead author of a study published today in Science.

The researchers can’t be certain that the tools were made and used by Paranthropus, because hominins from other genera—such as Homo habilis—also frequented the Nyayanga area. But it’s a strong possibility. 

The tools and teeth from Nyayanga were in sediments dated to between 2.6 and 3 million years old. Plummer suggests the tools may be from the upper end of that range, at around 2.9 million years old.

The large rock on the left is the source material for Oldowan artifacts. Hominins hammered sharp chips off the core rock to be used as tools.
Photograph by T.W. Plummer, J.S. Oliver, and E. M. Finestone, Homa Peninsula Paleoanthropology Project

Previously, the earliest Oldowan tools were 2.6 million years old, from the Afar region of Ethiopia, more than 800 miles to the north.

Although some even older stone tools, dated to 3.3 million years ago, have been unearthed at a single site in northwestern Kenya, the development of smaller and lighter Oldowan tools was a technological breakthrough.

Despite their rough appearance, Oldowan tools became widespread throughout much of Africa and even outside it, and they continued to be made and used for more than a million years by different Homo species. (Read about the oldest stone tools found outside of Africa.)

“Oldowan tools are a really important tool technology,” he says. “It’s salient both through space and through time.”

He hopes that future finds of Paranthropus fossils could cement the idea that this non-Homo hominin might have made the tools. What’s more, several later sites where Paranthropus fossils have been discovered near stone tools will have to be looked at anew: Maybe Paranthropus created the tools, not Homo.

Butchering hippos

Another interesting aspect of the Nyayanga discoveries is that hominins were butchering hippopotamuses at this time, says Bernard Wood, a palaeoanthropologist of George Washington University in Washington, D.C., who wasn’t involved in the study.

Some researchers have suggested butchering such large animals only occurred much later, after hominins had become larger and more adept at hunting.

Oldowan artifacts were found among fossilized hippopotamus skeletons at the Nyayanga site.
Photograph by T.W. Plummer, Homa Peninsula Paleoanthropology Project

“Nobody’s saying that they hunted these large animals, but maybe they came across them when they were dying and realised they could use the flesh and the bones,” he says. “People have speculated this was likely, but here there is good archaeological evidence.” (Read about mysterious stone tools unearthed in the Philippines.)

Human evolutionary biologist Neil Roach of Harvard University, who wasn’t involved in the study, adds that modern apes and monkeys, such as capuchins, make stone tools, so it might be expected that some non-Homo hominins used such objects.

“The old idea that tools appeared with Homo around two million years ago is well out the window, and this helps to slam it shut,” he says.


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