Cache of oldest bone tools reveals craftsmanship of early human ancestors

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05-03-2025

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Archaeologists have uncovered a collection of bone tools in northern Tanzania that were shaped by ancient human ancestors 1.5 million years ago, making them the oldest known bone tools by about 1 million years, according to new research.
Researchers have unearthed stone tools that date back to at least 3.3 million years ago, but before this discovery, the oldest known bone tools were found at European sites believed to be 250,000 to 500,000 years old.
The 27 fragments of limb bones, most from hippopotamuses and elephants, show evidence of having been sharpened and shaped, likely with the aid of stone pieces. Some of the bones reach up to nearly 15 inches (38 centimeters) long.
The bone tools, which all appear to have been systematically produced in the same style as one another, were found in Tanzania's Olduvai Gorge. The site is also where archaeologists have previously unearthed artifacts related to some of the first stone tools crafted by early hominins, or human ancestors who walked upright.
The new findings, presented in a study published Wednesday in the journal Nature, suggest that our ancient human relatives applied the same techniques they used to make stone tools to specific bones they selected from large mammals. Researchers believe the tools are evidence that hominins long ago were capable of abstract reasoning, or the ability to think critically by identifying patterns and making connections.
'This expansion of technological potential indicates advances in the cognitive abilities and mental structures of these hominins, who knew how to incorporate technical innovations by adapting their knowledge of stone work to the manipulation of bone remains,' said lead study author Dr. Ignacio de la Torre, scientist at the Spanish National Research Council's Institute of History and codirector of the Olduvai Gorge Archaeology Project, in a statement.
Olduvai Gorge is in East Africa, which is home to some of the earliest evidence of both tool production and use among early human ancestors. It is part of a UNESCO World Heritage site often referred to as the 'Cradle of Humankind' and is 'renowned for its unparalleled contribution to our understanding of early human evolution,' said study coauthor Jackson Njau, associate professor in the department of Earth and atmospheric sciences at Indiana University.
'As a Tanzanian native, I've been captivated since my high school days by the groundbreaking discoveries made at renowned Olduvai Gorge site in northern Tanzania,' Njau said. 'The iconic work of the famous archaeologists Drs. Louis and Mary Leakey, which discovered early human fossils … and the world's first human stone tools ignited my fascination and fueled the dreams of countless young students, myself included, who aspired to follow in their footsteps.'
The site has a timeline spanning 2 million to 20,000 years ago, and researchers have uncovered the remains of ancient human ancestors such as Homo habilis, Homo erectus and prehistoric Homo sapiens, or modern humans, he said. The archaeological record also includes cultural advancements and the evolution of toolmaking, Njau added.
During the Oldowan age, a time period named for stone artifacts found in the gorge, ancient humans used tools created by striking one rock against another to chip off flakes, a process that resulted in a basic shape. These simple tools were made between 2.7 million and 1.5 million years ago.
The hand ax emerged during a shift in early human innovation about 1.7 million years ago in a time called the Acheulean age that lasted until about 150,000 years ago. The large and heavy, pointed almond-shaped stones required complex technical ability called knapping, or chipping away small flakes to create sharp edges, for their production, de la Torre said.
The Olduvai Gorge bone tools were first spotted in 2018 during excavations carried out between 2015 and 2022. Researchers narrowed in on a specific gully in the gorge after first finding hominin teeth on the surface during a field survey between 2010 and 2011, which Njao helped lead with Robert Blumenschine, professor emeritus of evolutionary anthropology at Rutgers University in New Jersey.
Elephant bones resulted in the largest tools, ranging from 8.6 to 15 inches (22 to 38 centimeters) long and 3.1 inches to 6 inches (8 to 15 centimeters) wide, while the hippo bones made for slightly smaller tools spanning from 7 to 12 inches (18 to 30 centimeters) long and 2.3 to 3.1 inches (6 to 8 centimeters) wide.
The same knapping techniques were applied to bones made exclusively from the dense, strong long bones of large animals. The tools, mainly made from bones freshly collected from carcasses, shed 'new light on the almost unknown world of early hominin bone technology,' the study authors said.
'The tools show evidence that their creators carefully worked the bones, chipping off flakes to create useful shapes,' said study coauthor Dr. Renata Peters, associate professor at the University College London's Institute of Archaeology, in a statement. 'We were excited to find these bone tools from such an early timeframe. It means that human ancestors were capable of transferring skills from stone to bone, a level of complex cognition that we haven't seen elsewhere for another million years.'
The bones add new evidence that early hominin cultures were experiencing a technological transition about 1.5 million years ago, de la Torre said.
'Prior to our discovery, the technological transition from the Oldowan to the Acheulean was limited to the study of stone tools,' de la Torre said. 'This discovery leads us to assume that early humans significantly expanded their technological options, which until then were limited to the production of stone tools and now allowed new raw materials to be incorporated into the repertoire of potential artifacts.'
An advanced comprehension of toolmaking and the ability to apply it to different materials suggests that ancient human ancestors had greater cognitive abilities than previously believed, the researchers said.
Previous discoveries of bone tools have occurred in isolated instances across Europe and Asia, but the 27 bones found at Olduvai Gorge seem to imply mass production, the study authors said. While the bone tool kits found later in Europe, dated to 400,000 years ago, are much more refined, the Olduvai Gorge tools were more effective for heavy-duty tasks, Njau said.
While there is no direct evidence to show how the tools were used, the researchers said they believe hominins employed them to strip down animal carcasses for food and to produce new tools.
The researchers also don't know which specific human ancestor species made the tools because no hominin remains were found with the bones. But previous research conducted at the site has suggested that Homo erectus and the hominin species Paranthropus boisei lived in the region.
Human ancestors were likely inspired to make tools from bone due the abundance of animal carcasses available across the landscape, especially during seasonal migrations, Njau said, while rocks may have been harder to come by depending on where the hominins lived. But bone tools are scarcer in the archaeological record because organic material such as bone can break down more easily, he said.
Dr. Briana Pobiner, paleoanthropologist and research scientist in the Human Origins Program at the Smithsonian National Museum of Natural History, said the study underscores the importance that tools made from materials other than stone had for our ancestors — and how these artifacts can be 'essentially archaeologically invisible.' Pobiner was not involved in the study.
'That there is a collection of 27 bone tools, and not just one or a few, suggests that hominins 1.5 million years ago (at least in this one place) were able to successfully transfer their knowledge of how to knap stone to knapping bone,' Pobiner said. 'To me, this signals that toolmaking was becoming an increasingly important part of our ancestors' lives. And once again, we should be looking in museum collections for more evidence of hominin behavior — in this case, bone tool manufacture — earlier than we might have previously expected.'