A set of stone tools found in Kenya is the oldest of its kind, and one of the oldest known to have been made by ancient hominins. The find adds to the evidence for widespread tool use relatively early in human evolution.
The artefacts were found with two teeth belonging to hominins called Paranthropus. They weren’t thought to make tools because their teeth were well-suited to chewing food, but the new find suggests they actually did make and use stone tools.
The finds come from Nyayanga on the north-eastern shore of Lake Victoria in Kenya. Tom Plummer at Queens College, City University of New York first learned of them more than 20 years ago, when he was working at another archaeological dig nearby. There, team member Blasto Onyango at the National Museums of Kenya in Nairobi mentioned a different site with similar tools. “We surveyed,” says Plummer, “we saw some material on the surface”, but it took until 2015 to begin full excavations.
The team has since recovered 330 stone artefacts. They include the heavy cores of pebbles, used for pounding, and sharp cutting flakes that had been removed from them. The tools are a type known as Oldowan, named for Oldupai gorge in Tanzania where the first examples were found.
Based on analyses of the sediments in which the Nyayanga tools were found, and the types of fossils found with them, the team estimates they are between just over 3 million and 2.6 million years old. “We think it’s in the older end of that range,” says Plummer. This would make them the oldest Oldowan tools on record. Previously, the oldest known examples were those from Ledi-Geraru in Ethiopia, which are from 2.6 million years ago.
The Nyayanga tools were used to process a variety of foods, says Rahab Kinyanjui, also at the National Museums of Kenya. The team found bones of hippopotamus-like animals, some of which had cut marks on them, suggesting the tools were used for butchery. The heavier implements were also used to pound plant materials like tubers and fruit.
Finding evidence of Oldowan tool use this early in Kenya, and 1300km from Ledi-Geraru in Ethiopia, suggests stone tool use was already widespread, says Plummer. In line with this, stone tools have been found in Algeria from 2.4 million years ago.
The use of such implements is primarily associated with the Homo genus, which includes our own species Homo sapiens, as well as older ones like Homo erectus. The oldest purported Homo remains are 2.8 million years old, but none have been found at Nyayanga. The only hominin remains there so far are of Paranthropus.
Paranthropus lived alongside other hominins, including Homo, for over a million years. However, it is generally thought that they have no living descendants. Compared with other hominins from the same time, they looked less like us: in particular, they had very large teeth, perhaps for grinding up tough plant foods.
“The thing about Paranthropus is they’ve got a really specialised anatomy,” says Plummer. “They’ve got the biggest jaws and teeth of any primate that ever lived, for their weight.” He says it is unlikely that a tool-using animal would need such powerful chewing apparatus. Nevertheless, it is the only hominin found at Nyayanga so far, so he says it is worth seriously considering that Paranthropus made and used the tools.
Others are less hesitant. “People are very shy about saying that it was not Homo something, Homo habilis or whatever, making tools,” says Margherita Mussi of the Italo-Spanish Archaeological Mission at Melka Kunture and Balchit, based in Rome. She points out that several modern primates sometimes make crude stone tools, including chimpanzees and various monkeys. “So why not a Paranthropus?”
If that is true, it would fit with other evidence that species of Homo were not the only hominins that made stone tools. The oldest known stone tools of any kind, at 3.3 million years old, are from Lomekwi in Kenya. They are cruder than Oldowan versions and were made in a different way: by hitting rocks on the ground, rather than by hitting a rock held in the hand.
“We have no genus Homo at that time,” says Sonia Harmand at Stony Brook University in New York, one of the discoverers of the Lomekwi tools. “We already know that the first stone tools were probably not made by Homo.” Australopithecus species are likely candidates.
For the later Nyayanga tools, there were probably late Australopithecus, early Paranthropus and early Homo in the region. “We have to imagine it’s all these species probably sharing the same territory or the same environment at the same time,” says Harmand.
Studies like these suggest tool use goes back further than we thought, says Plummer. “We’re going to be pushing tool use further back in time,” he says. Furthermore, “tool use was more important earlier on than we realised”.
In line with this, Mussi and her colleagues showed last month that some hominins were making obsidian tools in organised “workshops” 1.2 million years ago, 500,000 years earlier than thought. “I think that we are systematically under-evaluating hominins,” says Mussi.
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