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We know that our ancient ancestors were creating stone tools as early as 3.3 million years ago. However, it has long been believed that implements made of bone were not being produced in the same systematic way until the Middle Pleistocene, when evidence begins to appear at sites in Eurasia from c.500,000 years ago onwards. Now, though, a new discovery has pushed this date back by over a million years.
A significant site
Olduvai Gorge in northern Tanzania is a place of enormous archaeological significance. Excavations began here in the 1930s, led by Mary and Louis Leakey, and over the years the area has produced a wealth of important palaeoanthropological discoveries, including multiple early hominin remains, as well as the ancient stone tools that gave name to the Oldowan industry, which was in operation from 2.6 to 1.5 million years ago. The latest discovery represents yet another valuable piece of the puzzle.
Between 2015 and 2022, the Olduvai Gorge Archaeology Project (OGAP) carried out extensive fieldwork at a site known as the T69 Complex, located in an area of the gorge called the Frida Leakey Korongo (FLK) West Gully. Over eight seasons, the OGAP team exposed an area of nearly 300m2 and uncovered thousands of artefacts and fossil remains, including an assemblage of 27 bone tools.
All of the bone tools came from a single horizon, which has been securely dated to 1.5 million years ago using radiometric and chronostratigraphic data. Other finds from this layer include almost 11,000 stone tools associated with the Acheulean culture, which began to replace the Oldowan from c.1.7 million years ago, as well as over 9,000 identifiable animal bones. The 27 bone tools identified were all, with one exception, made from fragments of the limb bones of large mammals, most commonly elephant and hippopotamus. Hippopotamuses are well represented in the general faunal assemblage at the T69 Complex, and it is thought that people may have been drawn to the site by an abundance of hippo carcasses. In contrast, elephant remains are relatively scarce here, leading researchers to suggest that perhaps these bones had been found elsewhere and brought to the site as shaped limb fragments.
Analysis of the bone tools determined they had been knapped using stone tools, with flakes removed in an intentional, systematic manner to produce hefty, sharp bone implements, some up to 38cm long. Several show the same pattern of modification to produce a particular design featuring one crescent-shaped end and one pointed end, with a notch in middle, perhaps intended to help the user grip the tool. The function of these objects is unknown, but given their size and shape they were probably intended for heavy-duty tasks, perhaps the butchery of large animal carcasses. This conclusion is supported by fracture patterns on some of the tools, reflecting percussive and compressive activities.
Understanding the toolmakers
The recently discovered assemblage pre-dates other evidence of systematic bone-tool production by around one million years, demonstrating that humans were intentionally selecting and shaping animal bones for tools much earlier than previously believed. No hominin remains have been found during excavations at the T69 Complex, so we do not have direct evidence for which species was responsible for the production of the bone tools. However, two species are known to have been present in the ancient Olduvai Lake basin at this time: Homo erectus and Paranthropus boisei. Hand-axe production has traditionally been attributed to Homo erectus, leading the researchers to conclude that this species can be considered the most likely candidate at present.
Regardless of who created the bone tools, their existence offers important information about early human cognition and behaviour. The assemblage provides evidence that the toolmakers possessed knowledge of both animal anatomy and the properties of different materials, in order to select the best type of bones for a particular purpose; the technological capabilities required to transfer stone-knapping skills to a new material with entirely distinct properties; and the capacity for advanced planning and social learning essential to produce tools repeatedly that fulfilled specific intended functions. The discovery also reflects a shift in the way early humans interacted with the animals of the African savannah. In earlier periods, these animals were categorised as hazards, competitors, or, later, sources of food, but it now seems that, from at least 1.5 million years ago, hominins were viewing other mammals as sources of raw material for tools, too. Just as the transition to seeing animals as protein sources marked a major step in human evolution, this is another important development.
Significantly, these were not the only developments occurring at the time. The bone-tool assemblage appears at a pivotal point in time, during the transition from the Oldowan tradition – a relatively rudimentary stone-tool industry, largely involving striking two rocks together to create sharp-edged flakes – to the more complex Acheulean, characterised by the production of large hand-axes, which required much greater technical ability. Previously, this critical advancement in hominin technologies and cognitive capabilities could only be investigated through the stone tools themselves. The discovery of bone toolkits offers a valuable new angle from which to explore the period in question.
One obvious question remains: why is other evidence of systematic bone-tool production not found until c.500,000 years ago? The researchers offer two potential explanations. The first is simple preservation bias: organic materials like bone do not survive as well as stone in the archaeological record. The second is a technological shift: perhaps, as stone-tool technologies improved, bone tools were viewed as less effective and fell out of favour. Further research is needed.
This discovery, published in Nature (https://doi.org/10.1038/s41586-025-08652-5), represents a milestone in archaeology. The bone tool assemblage from Olduvai Gorge challenges previous assumptions about the development of tool production and, consequently, the capacity for complex thinking and behaviour among ancient hominins. The unexpected find also serves as a reminder of the constant potential of new discoveries to reshape our understanding of the story of human origins.
Text: Amy Brunskill / All images: © CSIC-Pleistocene Archaeology Lab, unless otherwise stated
