The ancestors of humans started making tools about 3.3 million years ago. First they made them out of stone, then they switched to bone as a raw material. Until recently, the earliest clear evidence of bone tool making was from sites in Europe, dated to 400,000 years ago. But archaeologists have now found and dated bone tools in Tanzania that are a million years older.
The tools are made from the bones of large animals like hippos and elephants, and have been deliberately shaped to make them useful for butchering large carcasses.
The discovery of bone implements that are the oldest ever found, by far, casts light on human evolution. It shows that our hominin ancestors were able to think about and make this technology a lot earlier than anyone realised.
I am a scientist who co-directs a multidisciplinary research project team at the Olduvai Gorge in Tanzania, focusing on hominin evolution. Our project's main goal has been to investigate the changes in hominin technology and behaviour that happened between 1.66 million and 1.4 million years ago.
We're interested in this time period because it marks a pivotal change in human technology, from the rudimentary stone knives and cores of the Oldowan culture to the more advanced crafted stone handaxes of the Acheulean culture.
We found the Olduvai bone tools in 2018 and recently described them in the journal Nature. They show that by 1.5 million years ago, our ancestors (Homo erectus) had already developed the cognitive abilities required to transfer skills from making stone tools to making bone tools.
This leap in human history was a game-changer because it allowed early hominins to overcome survival challenges in landscapes where suitable stone materials were scarce.
Tools at Olduvai
Olduvai Gorge is a Unesco World Heritage site. It became well known in 1959 through the pioneering work of palaeontologists Louis and Mary Leakey, whose discoveries of early human remains reshaped our understanding of human evolution. The site offers an unparalleled window into human history, spanning nearly 2 million years.
Read more: Finds in Tanzania's Olduvai Gorge reveal how ancient humans adapted to change
Aside from fossilised bones, it has yielded the most detailed record of stone tool cultures in the world. It has documented the evolution from the simple chopping tools and stone knives of the Oldowan industry (about 2 million years ago) to the more advanced Acheulean tools (1.7 million years ago), such as handaxes, cleavers, picks and spheroids and then on - through arrowheads, points and blades (about 200,000 years ago) to the micro-blades of the Later Stone Age (about 17,000 years ago).
All these tools provide a glimpse into the ingenuity and cultural advancements of our early ancestors.
And now the picture has new detail.
Our team uncovered 27 ancient bone tools during excavations at the T69 Complex, FLK West site at Olduvai. We know how old they are because we found them securely embedded underground where they had been left 1.5 million years ago, along with thousands of stone artefacts and fossilised bones. We dated them using geochronological techniques.
Unlike stone, bone shafts crack and break in a way that allows the systematic production of elongated, well-shaped artifacts. Flaking them by hitting them with another object - a process called knapping - results in pointed tools that would be ideal for butchering, chopping and other tasks.
The knapped tools we found were made from large shaft fragments that came from the limb bones of elephants and hippos, and were found at hippo butchery sites. Hominins likely brought elephant bones to the site on a regular basis, and obtained limb bones from butchered hippos at the site itself.
What Homo erectus knew
The find shows that 1.5 million years ago, Homo erectus could apply knapping skills to bone. Homo erectus, regarded as the evolutionary successor to the smaller-brained Homo habilis, left a lasting imprint on history. Its fossils, found at Olduvai, offer a glimpse into a span of about a million years, stretching from 1.5 million to roughly 500,000 years ago.
Now we know that these hominins not only understood the physical properties of bones but also knew about skeletal anatomy. They could identify and select bones suitable for flaking. And they knew which animals had skeletons large enough to craft reliable tools after the animals' death.
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Read more: Large mammals shaped the evolution of humans: here's why it happened in Africa
We don't know exactly why they chose bones as a raw material. It may have been that suitable stone material was scarce, or they recognised that bones provided a better grip and were more durable.
Why haven't such old bone tools been found before? The answer is likely that they are destroyed by weathering, abrasion from water transport, trampling and scavenger activity. Organic materials don't always get time to fossilise. Also, analysts were not used to looking for bone tools among fossils.
This discovery will likely encourage researchers to pay closer attention to the subtle signs of bone knapping in fossil assemblages. This way we will learn more about the evolution of human technology and behaviour.
Jackson K Njau, Associate professor, Indiana University
