The discovery of the oldest stone tools to date could change our understanding of human evolution, says Matt Pope
Archaeologists have discovered stone artefacts in Kenya dating back over three million years, making them the oldest stone tools yet discovered. The finding pushes back the record of stone tools by 700,000 years. While the tools predate the earliest known representative of our own genus, Homo, it is not yet possible to pin down exactly which species created the tools.
However, the artefacts may provide a link between the kinds of stone tool used by chimpanzees and other primates for pounding and nut-cracking but which lack intentionally removed flakes and more sophisticated edged stone tools created by hominins. The findings, which add to a number of recent discoveries of the use of stone tools by early humans, could mean that the time has come for us to start considering whether all hominins used tools.
Unmodified stones of a suitable size can be used as tools, for example as hammers to break open nuts. But the use of sharp-edged flakes, hammered from the edge of a large rock, shows a sophisticated understanding of how rocks break and the fine motor skills to break them usefully. That’s why sharp-edged tools are so important as markers in the archaeological record and why they mark out hominin technology as distinct to that of other primates.
“The tools could be our first glimpse of a previously unknown phase in technological evolution.”
Until now, the oldest known stone artefacts are from around 2.6m years ago, discovered in Gona, Ethiopia. Tools from about 2.3m years ago have also been discovered at the sites of Hadar and Omo (both in Ethiopia) and Lokalalei in Kenya. The recent discovery was made not far from there at the archaeological site Lomekwi 3, situated to the west of Lake Turkana in Kenya.
While it is currently unknown which species of hominin made the ‘Lomekwian’ (the name the researchers have proposed for the find), the early human ancestor Kenyanthropus platyops was present in West Turkana at this time, and Australopithicus Afarensis remains have been found in east Africa from this period. Perhaps it’s now reasonable to consider that all hominin species used tools, made of either stone or other perishable material.
Given how common tool use is in other contemporary primates such as chimpanzees, we should consider that stone use might have a very deep prehistory. Perhaps back to, and maybe before, our evolutionary paths diverged. The tools from Lomekwi are significant as they provide a snapshot of early tool use.
In fact, the authors suggest that the tools could be our first glimpse of a previously unknown phase in technological evolution. This is because the tools produced at Lomekwi look different to the stone tools from the other sites, and also from the Oldowan, the early technologies from Olduvai Gorge, in Tanzania, which are about 1.9m years old.
One of the reasons Lomekwi tools are different from Oldowan technologies is that they are larger. It also seems like the Lomekwi produced their sharp flakes by pounding stones against a passive hammer or anvil, rather than through a freehand technique more often used in Oldowan technologies. The Lomekwi flakes also show more errors and indications of poorer flaking technique than that recorded for later Oldowan assemblages.
These features are compelling and provide a link between the kinds of gestures we see in the nut-cracking activities of chimpanzee stone tool-use behaviour, and the more precise and controlled freehand flaking of the later Oldowan technologies.
The authors are clear in stating that this discovery, however significant, only “marks a new beginning to the archaeological record” of stone tool use. When flaked stone tool use by primates began, or indeed how the makers of the Lomekwian might be related to our own genus Homo, are questions that remain to be answered.
History shows that studies that push back archaeological frontiers of knowledge are always, as they should, met with scepticism from fellow scientists. It will be interesting to see what scrutiny the Lomekwi finds come under now that they have been published. In fact, a study in 2010 reported bones exhibiting cut marks consistent with stone tools dating to 3.3m years in the Lower Awash locality of Dikika, Ethiopia. This would have pushed back the age of stone tool use at that time by 800,000 years.
However, these claims were confronted, with critics saying that other factors, such as trampling by herbivores, could have been responsible for the observed damage to the bones. Even a small degree of uncertainty was enough to place the finds under a cloud of ambiguity. Without the stone tools themselves or supporting evidence from other localities at the time, it simply wasn’t enough to push the widely accepted archaeological record of tool use beyond 3m years.
Five years on the landscape has changed. The genus Homo has now been dated back to 2.8m years, half a million years older than previously thought. Recent work has also indicated that it would have been possible for these early hominins to makes such tools, as they could use their hands in a manner similar to modern humans.
The ‘Lomekwian’ will no doubt come under close examination in the days and months ahead, but it arrives into a wider discipline which can accommodate it theoretically and, to a degree, expected its arrival.
In light of the finds, we might see a reassessment of the Dikika bones, and more focus on deposits of this age more generally across east Africa, and beyond. The immediate impact of this new work will be to reinvigorate research which pushes boundaries, searching in the places and in the time scales where the archaeological record is currently unknown.
First published by The Conversation