Hominins have been using stone tools to access meat from Animal carcases for at least 2.6 million years, and this use of stone tools is also presumed to have helped them switch to a significantly more carnivorous diet. Logically, a Hominin which can use stone tools to hunt large Animals should also be able to make tools from the bones of those Animals, but bone tools have a much more limited record than their stone counterparts.
A number of bone-objects from archaeological sites in Africa dated to between 2.5 and 0.8 million years ago have been interpreted as having been modified by use as tools, for such purposes as digging or Termite fishing, but do not appear to have been deliberately shaped prior to use. A few purpose modified tools have been repoted from Olduvai Gorge in Tanzania, but these were surface finds, lacking the context from which they could be dated. Bone tools are also known from the Konso site in Ethiopia, including a bone handaxe which has been dated to 1.4 million years ago. Bone tools start to appear across Eurasia around 500 000 years ago, and highly shaped bone tools, such as spear and arrow points, barbed points, awls and needles, appear in Africa about 90 000 years ago, spreading to Eurasia around 45 000 years ago.
In a paper published in the journal Nature on 5 March 2025, Ignacio de la Torre of the Instituto de Historia of the CSIC-Spanish National Research Council, Luc Doyon of the Université de Bordeaux, Alfonso Benito-Calvo of the Centro Nacional de Investigación sobre la Evolución Humana, Rafael Mora of the Facultat de Lletres at the Universitat Autonoma de Barcelona, Ipyana Mwakyoma, also of the Instituto de Historia of the CSIC-Spanish National Research Council, Jackson Njau of the Department of Earth and Atmospheric Sciences at Indiana University, and the Stone Age Institute, Renata Peters of the Institute of Archaeology at University College London, Angeliki Theodoropoulou, again of the Instituto de Historia of the CSIC-Spanish National Research Council, and Francesco d’Errico, also of the Université de Bordeaux, and of the SFF Center for Early Sapiens Behaviour at the University of Bergen, describe an assemblage of bone tools from a horizon at Olduvai Gorge Bed II, which has been dated to 1.5 million years ago.
The tools form part of an assemblage identified as the T69 complex, were derived from a layer between Middle and Upper Bed II, in the Frida Leakey Korongo West Gully at Olduvai Gorge, which has been radiometrically dated to 1.5 million years ago. T69 complex materials have been derived from six tranches, the bulk of the material comprising early Acheulean stone tools. A total of 10 900 stone tools larger than 2 cm, and over 41 000 smaller artefacts have been recovered, mostly made from a local quartzite.
In addition to the tools, the assemblage contains abundant Vertebrate fossils, including 9419 identified bone fragments and 13 413 unidentified fragments. Many of the identifiable remains can be attributed to Fish, Crocodiles, and Hippopotamuses, suggesting that 1.5 million years ago, the site was close to water. The majority of the large Animals are Bovids and Hippopotamuses, with some relatively intact Hippopotamus carcasses present. Other large Animals present include Equids, Suids (Pigs), Rhinoceros, and Elephants. Hippopotamus bones are the most abundant, and many of these show signs of deliberate modification.
The faunal elements of the T69 assemblage, including bone tools, are excellently preserved, something not common at Middle Pleistocene sites, allowing for careful documentation and analysis of the material present. De la Torre et al. identify 27 artefacts as unequivocal stone tools, ruling out other forms of damage such as Carnivores gnawing, Crocodiles biting, trampling and fracturing to access marrow; in fact, Carnivore bones are very rare in the T69 assemblage, and the only signs of bone-modification by Carnivores are two possible tooth marks.
Tools are identified as bones with multiple fragments removed, which lack the striations associated with trampling. Experimental breaking of large Mammal bones to recover marrow failed to produce similar flaking. Patterns of breakage consistent with marrow-extraction are present on many bones present in the faunal assemblage, suggesting that this was something done by the Hominins here. This seldom results in more than two or three flakes being removed, whereas the 'tools' have an average of 12.9 flaking scars, typically arranged contiguously and preferentially on their lateral edges.
Twenty seven bone tools were recovered during excavations at Frida Leakey Korongo West Gully, eighteen of which are attributed to Mammals weighing more than two tonnes. Sixteen of these are identifiable, including eight tools made from Elephant bones, six tools are made from the bones of Hippopotamus, and two from the bones of large Bovids. Thus, in an assemblage dominated by Bovid bones, where 169 taxa are recorded and Elephant remains make up about 1.1% ot the total, more than half the tools are made from Elephant bones. One of the tools is made from the proximal portion of the radius of a large Bovid, all the others from long portion of limb bones, predominantly the femora, tibiae and humeri.
The Frida Leakey Korongo West Gully tools represent a set of technological and behavioural innovations previously unrecorded in Hominins of this antiquity. The tools are relatively 'fresh', which is to say they were apparently buried quite soon after being made, and do not show signs of having sat on the surface and subject to weathering. The Hippopotumus bone tools all appear to have been made from fresh bone (i.e. from Animals which had died shortly before the tools were made), but some of the Elephant bone tools appear to have been made from bones partially weathered before flaking occurred, suggesting that old Elephant bones were recognised as a valuable resource and collected separatley from scavenging carcases for food. Elephant bone tools range from 22 to 38 cm in length and from 8 to 15 cm in width, making them the largest in the assemblage. Hippopotamus bone tools are slightly smaller, 18 to 30 cm in length and 6 to 8 cm in width.
Elephant bone tools also show more working, showing on average 17.3 flake removal scars, compared to an average of 13.3 scars on Hippopotamus bone tools. Among the fifteen tools made from unidentified Animals, seven are comparable to Elephant or Hippopotamus bone tools in size, with similar numbers of scars, while eight are smaller, with an average of six flaking scars. The preferred method of tool making appears to have been to first remove large flakes to give the tools its shape, then remove smaller flakes to regularize the edge surfaces. Experimentally braking bones for marrow-extraction produced scars significantly shorter than the initial flaking used in tool production at Frida Leakey Korongo West Gully, indicating deliberate intent from the outset. The shape of the scars is compatible with the use of hand-held hammerstones, although these would have needed to be large and heavy.
Six of the large-Mammal bone tools show a recurrent shape, with one crescent-shaped end and one pointed end, combined with a large notch on the middle part of the tool. This was achieved using an average of 16.8 flake removals, the majority of which are associated with the creation of the notch. The pointed end of the tool corresponds to the robust part of the diaphysis (middle section) of the bone, which the rounded end appears to be derived from the metaphysis (wider, end-part) of the bone.
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