NEW YORK (AP) — Archaeologists in Kenya have unearthed some of the oldest stone tools ever, but who used them is a mystery.
In the past, scientists assumed that our direct ancestors were the only toolmakers. But two large fossil teeth found along with the tools at the Kenyan site belong to an extinct human cousin known as Paranthropus, according to a study published Thursday in the journal Science.
This adds to evidence that our direct relatives in the Homo lineage may not have been the only tech-savvy creatures during the Stone Age, said study author Rick Potts, director of the Smithsonian’s Human Origins Program.
“Those teeth open up an amazing whodunit – a real question, well, who were these first toolmakers?” Potts said.
The tools date back to about 2.9 million years ago, when early humans used them to butcher hippos for their meat, the researchers report.
Older stone tools have been found in Kenya, dating back about 3.3 million years, long before our own Homo ancestors appeared. Those tools were a bit simpler and have only been found in one place so far, said Shannon McPherron, an archaeologist at Germany’s Max Planck Institute for Evolutionary Anthropology who was not involved in the study.
The latest discovery corresponds to a much larger tradition known as the Oldowan toolkit. For more than a million years of prehistory, the same types of tools appear across Africa and beyond, Potts said, showing that they really caught on with early humans.
They held a rock in one hand and hit it with another, breaking off thin, razor-sharp flakes, said anthropologist Kathy Schick of the Stone Age Institute in Indiana, who was not involved in the study.
The rocks and flakes allowed early humans to cut and crush a wide variety of materials, said lead author Thomas Plummer, an anthropologist at Queens College of the City University of New York. And the tools from the Kenya site — likely the oldest Oldowan tools found to date — suggest this gave them an advantage in an important area: food.
The site, known as Nyayanga, is a lush, hilly landscape on the shores of Lake Victoria. Since excavations there began in 2015, researchers have found a trove of artifacts and animal bones, along with the two Paranthropus teeth.
Cut marks on several hippopotamus bones show they were carved for their meat, which would have been eaten raw like hippopotamus steak tartare, Plummer said. Early humans probably also used their tools to crack open antelope bones for their fat marrow inside, and to peel the outer shells off tough plant roots, the authors concluded.
“Stone tools, even at this very early period, allow them to extract a lot of resources from the environment,” Plummer said. “If you can butcher a hippo, you can butcher pretty much anything.”
In the past, it was easy to assume that our direct ancestors were the ones using these tools, Plummer said. But the teeth make it hard to rule out that other early humans picked up their own tools, researchers said — even extinct cousins like Paranthropus, with their big teeth and little brains.
The mystery will be difficult to solve.
After all, we can’t say for sure whether Paranthropus used these tools or just happened to die in the same spot, Schick said: “When we find hominin fossils with stone tools, you always have to ask, Is this the dinner?” or the restaurant?”
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