Humans
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A new proposal offers an easy route for our ancestors to have made one of their earliest and most important technological advances. Instead of some australopithecine genius coming up with the idea of carefully striking stones to produce sharp blades, early humans may have begun by using those they found precut. The idea might refashion how we envisage a step in our development as more important than any specific tool.
“The secret is to bang the rocks together, guys,” a pan-galactic announcer in The Hitchhiker's Guide To The Galaxy tells any newly sentient beings who have stumbled on his broadcast. But what if it’s not the start? What if banging rocks together is a later stage of technology after finding sharp rocks and putting them to effective use?
A big step in the story of human advancement begins with the use of sharp tools that allowed hominins to kill larger prey than their puny strength would have allowed, and to cut it up for transport or fair distribution.
However, the conventional version of this story, which begins with hitting large stones with small stone hammers to produce cutting instruments, now faces a challenge. A team of anthropologists thinks that many sharp stones were lying around the plains of Africa naturally, and our ancestors used these – perhaps after literally stumbling on one and cutting themselves – before learning to make more.
“I don’t think it was a ‘Eureka!’ moment whereby hominins first made a sharp stone flake by intention or by accident and then went to look for something to cut,” said Professor Metin Eren of the Cleveland Museum of Natural History in a statement. “There is no reason to produce sharp stone tools unless the need to cut is already in place.”
Stones with a sharp edge, but also well suited to be held in the hand – which the team calls “naturaliths” – are abundant where suitable rocks are present, the team argues. “Naturaliths can be, and are being, endlessly produced in a wide range of settings and thus may occur on the landscape in far greater numbers than archaeologists currently understand or acknowledge,” they write.
Rocks washed into fast-running streams or trampled on by herds of hoofed animals or elephants can break against each other, the authors point out, and some have a tendency to do so in ways that produce sharp edges. The team notes that naturaliths are common even in Antarctica, where there is no possibility they were made by ancient primates.
Professor Michelle Bebber was struck by the abundance of naturally produced sharp rocks in Oman. “It is quite astonishing… natural knives were likely readily available to our hominin ancestors,” said Bebber.
Dr Emma Finestone noted that sites where we have found evidence of early hominins processing food often occur close to sources of naturaliths. “A hominin could have picked up and used a naturally sharp rock to process a carcass or plant material that might have been difficult to access using just their hands and teeth,” the researcher explained.
From there, it is not hard to imagine tribes of early humans coming to rely on naturaliths. Only when the local resource had been exhausted, perhaps blunted from overuse, might deliberate manufacturing have begun. Alternatively, someone with a usable, but inferior, stone might have been inspired to try to reproduce the local favorite.
We now know that tool use is very widespread among animals – even some fish do it – but one thing humans still seem to have to ourselves (unless we assist) is secondary tool use: using a tool to make another tool. More than fire or language, crossing the threshold to secondary tool use might be the thing that really made us who we are. Put like this, it makes sense that to take such a difficult leap we needed a runup, such as thousands of years of using naturaliths might have provided. Even naturalith use may have developed from bone tools that started with the breaking of large prey animals’ bones.
The extra protein the knives made available would have come in handy – arguably helping brains to grow – but the secondary tool precedent may have opened up a world of new possibilities in our ancestors’ minds.
“This is the most parsimonious hypothesis for the origin of hominin stone technology to date,” said Eren. “But parsimony is not necessarily correct – archaeologists now need to test our hypothesis and search for naturalith use by hominins between 3 and 6 million years ago. It is an exciting prospect… if hominins are using naturally sharp rocks as knives, then the archaeological record is going to get a whole lot older.”
Telling naturaliths from deliberately knapped stones – particularly at the start of humanity’s development of stoneworking – may present a challenge, but the authors propose a number of lines of research that could be useful
There are reasons beyond curiosity to want to know if Eren, Bebber, Finestone, and co-authors are right. The “cumulative culture” they describe presents a profound challenge to the popular story of how major scientific developments occur. Instead of a lone genius doing all the important work – and deserving all the profits – progress may always have depended on small contributions of many people and the natural environment.
The study is published in Archaeometry.
