For those about to rock

Humans are expert tool-makers, and as far back as 2.6 million years ago our stone age relatives were getting there too. That’s according to an analysis of 300 stone artefacts – including sharp-edged rock flakes and the rocks they have been chipped from, known as “cores” – published in the journal PNAS.

The new trove of artefacts was unearthed in Ethiopia’s Afar Basin, a region that rocketed to fame in 1974 when the 3.2-million-year-old remains of our ancient relative “Lucy” (Australopithecus afarensis) were discovered.

The new site – known as Bokol Dora 1 (BD 1) – lies just five kilometres away from the location of one of oldest fossil remains of our own genus, Homo, a lower jaw that is 2.8 million years old.

Stone artefacts are the best evidence available of the early cognitive abilities of prehistoric humans. 

But discoveries in recent years show that other early hominins, lines that pre-dated the Homo lineage, got in on the act too. Primitive stone tools from the Lomekwi 3 site in Kenya, for instance, date to 3.3 million years ago.

Modern primates – chimpanzees and capuchin monkeys – are also known to fashion rudimentary tools.

But unlike the earlier Lomekwian tools, those from BD 1 show signs of systematic manufacture, says archaeologist David Braun from George Washington University in Washinton DC, US, who spearheaded the excavations and analysis with local archaeologists Niguss Baraki of Addis Ababa University, Blade Engda from the Ethiopian Authority for Research and Conservation of Cultural Heritage, and others.

Braun and his team compared the flakes and cores with stone artefacts from the Lomekwian site and younger locations in Africa.

He initially expected the tools to be intermediate between the older Lomekwian tools, and the more recent “Oldowan” tools used by Homo habilis. Instead, he found that they clearly belonged to the latter group.

“The material from 3.3 million years ago looks a lot more like the materials that we see even made by modern primates,” says Braun. He points to capuchin monkeys that “accidentally” make tools.

Lomekwian tools were made by bashing two rocks together to create flakes with sharp edges. The BD-1 tools were, too, but they show signs that whoever made them seemed to know what they were doing in a more repeatable way, says Braun.

“By 2.6 million years ago, they were beginning to understand the relationship between the folk physics of where to strike something, and how hard to hit it, and what angles to select,” he says. 

The tool-makers were also aware that not all rocks were equal when it comes to fashioning a blade, however rudimentary.

By combing through ancient cobble beds from the same time and region, Braun and his team found that suitable rocks – predominantly rhyolite – were overrepresented in the tool sample.

“They’re specifically selecting those rocks that they can make these tools out of, and even though other rocks are more abundant, they are not selecting those,” he says.

Archaeologist Mark Moore from the University of New England in Armidale, Australia, who was not involved in the study, commends the research.

“First-rate fieldwork and analysis like this is crucial for helping us understand what is one of the most important processes in the evolution of our species — the invention of technology,” he says.

The BD 1 tools mark a point where the technology is firmly embedded in the culture and continues to improve as time goes on, according to the analysis.

What happened prior to that is still up for debate. Because the tools are so distinct from the Lomekwian ones, Braun suspects that early hominins may have invented tool-making multiple times.

“We tend to think of these things as a sort of trajectory through time, but it is quite possible that there were lots of fits and starts of technology appearing and disappearing and then appearing and disappearing,” says Braun.

To really answer the question of whether the BD 1 tools – and later Oldowan artefacts – are improvements on Lomekwian tools, or an entirely independent invention, the intervening archaeological record will need to be filled.

“We really need more sites from that key period 3.3 million years ago, and from the nearly 700,000-year gap between Lomekwi 3 and BD 1,” says Moore. “Those sites may exist somewhere, and they hold a key missing part of this technological story.”

Related reading: How to uncover an ancient rocks age

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