On the shores of Lake Victoria in Kenya, a short valley extends south towards the looming Mount Homa. From it, an international team of archaeologists recently uncovered some of the oldest stone tools ever found as well as the oldest remains of one of our early cousins, Paranthropus—a genus we think co-existed with our direct ancestors.
The ancient tools discovered along the banks 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.
Using a combination of dating techniques, including the rate of decay of radioactive elements, reversals of Earth’s magnetic field, and the presence of certain fossil animals whose timing in the fossil record is well established, the research team was able to date the items recovered from Nyayanga to between 2.58 and 3 million years old.
“Though multiple lines of evidence suggest the artifacts are likely to be about 2.9 million years old, the artifacts can be more conservatively dated to between 2.6 and 3 million years old,” lead study author Thomas Plummer of Queens College, research associate in the scientific team of the Smithsonian’s Human Origins Program, said in a statement.
In the excavations at the site, 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 ancestors made the tools.
“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.”
“With these tools, you can crush better than an elephant’s molar can and cut better than a lion’s canine can,” Potts said. “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.”
“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.”
The Nyayanga deposits provide a glimpse into an ancestral world that’s possibly radically different from any we had pictured. In doing so, they’ve raised even more questions about hominin evolution.