Museum Curator Co-Authors New Research on First Stone Tools
CLEVELAND—February 9, 2023—Roughly 2.9 million years ago, along the shores of Lake Victoria in Kenya, early human ancestors used some of the oldest stone tools ever found to butcher hippos and pound plant material, according to new research led by scientists affiliated with Queens College, City University of New York; the Smithsonian’s National Museum of Natural History; the Cleveland Museum of Natural History; the National Museums of Kenya; and Liverpool John Moores University.
The study, published today, February 9, in the journal Science, presents what are likely to be the oldest examples of a hugely important Stone Age innovation known to scientists as the Oldowan toolkit, as well as the oldest evidence of hominins consuming very large animals. The artifacts are conservatively dated to between 2.6 and 3 million years old. Excavations at the site, named Nyayanga and located on the Homa Peninsula in western Kenya, also produced a pair of massive molars belonging to the human species’ close evolutionary relative Paranthropus. The teeth are the oldest fossilized Paranthropus remains ever found.
Dr. Emma Finestone, Assistant Curator of Human Origins at the Cleveland Museum of Natural History, is part of the group of scientists, led by Dr. Thomas Plummer of Queens College, CUNY, who made this groundbreaking discovery. Dr. Finestone uses archaeological and paleoanthropological evidence to investigate behavioral innovations, early technology and toolmaking, and the adaptive shifts that enabled human ancestors to spread around the globe. Dr. Finestone led the analysis of the stone tools recovered from Nyayanga.
“The ability to make and use stone tools was an important breakthrough in our evolutionary history,” Dr. Finestone said. “However, many aspects of the origin of stone tools remain a mystery. For example, we don’t know definitively who made the earliest tools, what tasks the tools were used for, or how deep in time Oldowan technology extends. Nyayanga offers a glimpse into some of these big questions in human evolution. Finding Paranthropus alongside early stone tools is especially intriguing because it’s often assumed that Oldowan tools represent a technological breakthrough for our ancestors in genus Homo, not our evolutionary cousins Paranthropus.”
Whichever hominin lineage was responsible for the tools, the artifacts were found more than 800 miles from the previously known oldest examples of Oldowan stone tools—2.6-million-year-old tools unearthed in Ledi-Geraru, Ethiopia. This discovery greatly expands the area associated with the earliest origins of Oldowan technology. Further, the stone tools from the site in Ethiopia could not be tied to any particular function or use, leading to speculation about the earliest uses of the Oldowan toolkit.
Through analysis of the wear patterns on the stone tools and animal bones discovered at Nyayanga, Kenya, the team responsible for the discovery determined that these stone tools were used by early human ancestors to process a wide range of materials and foods, including plants, meat, and even bone marrow.
The Oldowan toolkit includes three types of stone tools: hammerstones, cores, and flakes. Hammerstones can be used for hitting other rocks to create tools or for pounding other materials. Cores typically have an angular or oval shape. When struck at an angle with a hammerstone, the core splits off a piece, or flake, that can be used as a cutting or scraping edge or further refined using a hammerstone. From 2015 to 2017, a series of excavations at Nyayanga yielded a trove of 330 artifacts identified as part of the Oldowan toolkit, as well as 1,776 animal bones and the two hominin molars identified as belonging to Paranthropus.
“Because of my interest in early stone-tool behaviors, I began working at Nyayanga from the first year of excavations,” Dr. Finestone said. “At the time, we didn't yet know how important the site would become to understanding early stone tools. As our work progressed, we continued to unearth more and more exciting fossils and artifacts, all the way up to the final hours of the 2017 field season. On our final day at Nyayanga, as we raced against a thunderstorm to record the last stone tools and fossilized bones from a butchered hippo, we uncovered a Paranthropus molar alongside it.”
Compared to the only other stone tools known to have preceded them—a set of 3.3-million-year-old artifacts unearthed at a site called Lomekwi 3, just west of Lake Turkana in Kenya—Oldowan tools represented a significant upgrade in sophistication. Oldowan tools were systematically produced and often fashioned using a method known as “freehand percussion.” In this technique, which requires significant dexterity and skill, the core was held in one hand and then struck with a hammerstone wielded by the opposing hand at just the right angle to produce a flake.
By contrast, most of the artifacts from Lomekwi 3 were created through the use of large stationary rocks as anvils, with the toolmaker either banging a core against the flat anvil stone to create flakes or setting the core down on the anvil and striking it with a hammerstone. These more rudimentary modes of fabrication resulted in larger, cruder, and more haphazard-looking tools.
Over time, the Oldowan toolkit spread all the way across Africa and even as far as modern-day Georgia and China. It was not meaningfully replaced or amended until some 1.7 million years ago, when the hand-axes of the Acheulean first appeared.
As part of their study, the researchers conducted microscopic analysis of wear patterns on the stone tools to determine how they were used. They also examined any bones exhibiting potential cut marks or other kinds of damage that might have come from stone tools.
The site featured at least three individual hippos. Two of these incomplete skeletons included bones that showed signs of butchery, including a deep cut mark on one hippo’s rib fragment and a series of four short, parallel cuts on the shin bone of another. Additionally, antelope bones showed evidence of hominins slicing away flesh with stone flakes or of having been crushed by hammerstones to extract marrow.
The analysis of wear patterns on 30 of the stone tools found at the site indicated that they had been used to cut, scrape, and pound both animals and plants. Because fire would not be harnessed by hominins for another 2 million years or so, these stone-tool makers would have eaten everything raw, perhaps pounding the meat to make it easier to chew.
Using a combination of dating techniques, including the rate of decay of radioactive elements, the timeline of 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.
The discovery of teeth from the muscular-jawed Paranthropus alongside these stone tools begs the question of whether it might have been that lineage rather than the Homo genus that was the architect of the earliest Oldowan stone tools, or even whether multiple lineages were making these tools at roughly the same time.
The excavations informing this study offer a snapshot of the world humans’ ancestors inhabited and help illustrate the ways that stone technology allowed these early hominins to adapt to different environments and, ultimately, give rise to the human species.
“Nyayanga represents a critical time in human evolution. During this period, we have early stone tools and multiple lineages of hominins who may have been making and using tools alongside one another. They were using tools for a diversity of tasks, even butchering hippos with sharp flakes and durable pounding tools,” Dr. Finestone said. “I am very excited to share this research, and I’m equally excited to return to the Homa Peninsula this summer and continue working to see what else Nyayanga has in store.”
This research was supported by funding from the Smithsonian, the Leakey Foundation, the National Science Foundation, the Wenner-Gren Foundation, the City University of New York, the Donner Foundation, and the Peter Buck Fund for Human Origins Research.
“Dr. Finestone is redefining her field, and as a member of our interdisciplinary research team, she is helping us reframe our understanding of humanity’s past, present, and future,” said Sonia Winner, President & CEO of the Cleveland Museum of Natural History. “Our museum is in the midst of a major transformation project, and Dr. Finestone’s research is contributing invaluable insights to new conversations regarding human origins and evolution.”
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