2.9 million-year-old tools found in Kenya stir up a ‘fascinating whodunnit’

The stone tools could likely be the oldest evidence of Stone Age innovation.
Fossil hippo skeleton and associated Oldowan artifacts at the Nyayanga site in July 2016.
Fossil hippo skeleton and associated Oldowan artifacts at the Nyayanga site in July 2016. T.W. Plummer, Homa Peninsula Paleoanthropology Project

An international team of archaeologists recently uncovered some of the oldest stone tools ever found. The ancient tools, discovered along the banks of Lake Victoria in Kenya, are likely the oldest evidence of both an important Stone Age innovation called the Oldowan toolkit and of hominins consuming very large animals. The findings were published on February 9 in the journal Science

The Oldowan toolkit includes three types of stone tools: hammerstones for hitting other rocks or creating tools that pound, cores that are angular or oval shaped and split off pieces of material, and flakes used as a cutting or scraping edge.

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The team says that while there is solid evidence that the artifacts are likely about 2.9 million years old, a more conservative estimate is between 2.6 and three million years old. 

In the excavations at the site named Nyayanga on western Kenya’s Homa Peninsula, the team also found a massive pair of molars that belong to Paranthropus– a genus of close evolutionary relatives of modern humans. These teeth are the oldest fossilized Paranthropus remains found by scientists. Their presence at a site with so many stone tools has sparked a mystery about which human ancestor made the tools.

Examples of an Oldowan percussive tool, core, and flakes from the Nyayanga site. CREDIT: T.W. Plummer, J.S. Oliver, and E.M. Finestone, Homa Peninsula Paleoanthropology Project.

“The assumption among researchers has long been that only the genus Homo, to which humans belong, was capable of making stone tools,” said Rick Potts, a co-author of the study from the Smithsonian National Museum of Natural History, in a statement. “But finding Paranthropus alongside these stone tools opens up a fascinating whodunnit.”

Whichever human ancestor was responsible for building these tools was more than 800 miles away from the previously known oldest examples of Oldowan stone tools. These 2.6 million year old tools were uncovered in Ledi-Geraru, Ethiopia in 2019 and this new finding expands the region associated with Oldowan technology’s earliest origins. 

“With these tools you can crush better than an elephant’s molar can and cut better than a lion’s canine can,” said Potts. “Oldowan technology was like suddenly evolving a brand-new set of teeth outside your body, and it opened up a new variety of foods on the African savannah to our ancestors.”

The team analyzed the wear patterns on the stone tools and animal bones found near them, which led them to  believe that the tools were used to process various materials and foods, including plants, meat, and possibly bone marrow.

[Related: Ancient humans used mastodon bones to hunt the giant beasts.]

Among the 1,776 fossilized animal bones the team found 330 artifacts which showed signs of butchery. At least three individual hippos were found at the site and two of the incomplete skeletons had bones that showed signs of butchery–a deep cut mark on one hippo’s rib fragment and four short, parallel cuts on the shin bone of another hippo.

“Stone tools are allowing them, even at this really early date, to extract a lot of resources from the environment,” study co-author Thomas Plummer from City University of New York’s Queen’s College told the Associated Press. “If you can butcher a hippo, you can butcher pretty much anything.”

While the team says it will be difficult to solve the mystery of which ancestor species made the tools, the excavations in this study offer an important window to the past world of humans’ ancestors. The findings also show how stone technology allowed early hominins to adapt to different environments,eventually giving rise to today’s humans.

“East Africa wasn’t a stable cradle for our species’ ancestors,” Potts said. “It was more of a boiling cauldron of environmental change, with downpours and droughts and a diverse, ever-changing menu of foods. Oldowan stone tools could have cut and pounded through it all and helped early toolmakers adapt to new places and new opportunities, whether it’s a dead hippo or a starchy root.”