Israelis Crack 2-million-year-old Mystery About Stone Tools

Chopping tools were the real original Swiss army knife of the archaic human set, says Prof. Ran Barkai, but nobody knew what they were used for – until now

Ruth Schuster
Ruth Schuster
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Researchers from the Sonia and Marco Nadler Institute of Archaeology at Tel Aviv University unraveled the function of flint tools known as 'chopping tools'
Using a 'chopping tool' the way it was meant to beCredit: Ran Barkai
Ruth Schuster
Ruth Schuster

Starting about 2.6 million years ago, no archaic human would leave the cave without one. Archaeologists called these flint implements “chopping tools,” even though their actual use remained hotly debated. They weren’t the first stone tools ever used by hominins, but were the earliest known to be produced in a standardized fashion: the outer layer of the rock was left unmolested, and one end was knapped to have a sharp edge. The hominin would, presumably, grab the non-sharpened end and hit things with the edge.

Chopping tools were the implement that would be longest in use. They went everywhere archaic humans would go, for over 2 million years, throughout the Oldowan and Acheulean cultural complexes.

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The question is why. What function did chopping tools serve early humans, and for so long – during which time more sophisticated tools were developed, not least the hand ax? Some researchers have, and still do, believe these signature chopping tools were nothing more than the cores from which flint flakes were produced.

Not so. Chopping tools were apparently used to efficiently break long bones of animals to extract and eat the marrow, argue Flavia Venditti of the University of Tübingen and University of Rome, Stella Nunziante-Cesaro and Jacopo Tirillò from the University of Rome, and Aviad Agam and Prof. Ran Barkai from Tel Aviv University, in a groundbreaking study published Tuesday in PLOS One.

Their study was based on 53 chopping tools found at Revadim, a prehistoric site in Israel, but their findings likely apply to all chopping tools everywhere in the Old World, Barkai tells Haaretz.

Specifically, their analyses – including of organic residue still extant on the extraordinarily well-preserved tools – concluded that most had been used to chop hard and medium materials, such as bone, most likely for marrow extraction.

Chopping tools found at RevadimCredit: Ran Barkai
The result of using a chopping tool on a bone to get at its marrowCredit: Ran Barkai

The team agrees that the chopping tools could have been cores too, as usable flakes were struck for them while shaping the working edge, but they had a real purpose in exploitation of prey.

“People thinking they’re just cores are underestimating the abilities of prehistoric people,” the professor suggests. “They think Homo habilis and erectus couldn’t plan three steps ahead and have a concept of a tool that could be manufactured by repetitive production – they don’t believe they had a culture that could create standards of tool production.” It seems they did.

The earliest toolkit

To be clear, the chopping tool wasn’t the earliest stone implement used by archaics. Over 3.3 million years ago, hominins about halfway between the chimp and modern human began to use rather large, cumbersome rocks as tools. They were crude, nonstandard and could weigh well over a kilogram and sport signature fracture patterns, which is how they’re distinguished from just rocks.

It bears adding that we don’t know what these earliest tools were used for – hammering in some way, we figure.

Then, about 2.6 million years ago, Homo habilis, or somebody of that ilk, invented the chopping tool. It was a giant step up for our cognitive abilities. Basically, the chopping tool is a pebble that isn’t changed – except for one end, which is knapped to produce one sharp, massive edge.

Prof. Ran Barkai experiments with chopping toolsCredit: Ran Barkai

“Chopping tools went everywhere out of Africa. They appear all over the Old World – everywhere Homo habilis and Homo erectus reached. Until the time of the Neanderthals and Homo sapiens, it was an important part of the human toolkit,” Barkai says.

Even the handy hand ax, developed about 1.8 million years ago (800,000 years after the chopping tool) and itself used for hundreds of thousands of years, didn’t achieve that kind of longevity. And everywhere it went, the chopping tool had the same form: convenient handhold and that one sharp edge (though some examples of chopping tools were bifacial).

In any case, over the decades, archaeologists tended to relate to chopping tools in the context of cores – the team notes the definition by some as “chopper-cores.” Some researchers such as Mary Leakey did detect that choppers were “heavy duty tools,” but others argued they were just cores – the by-products of knapping the stone to get sharp flakes.

Or, one could argue that chopping tools remained in use for over 2 million years because they were smashing for the purpose they served – which Barkai and the team suggest was, chiefly, to break the long bones of animals to get at their marrow.

Why wouldn’t hominins use any old rock to break a bone to get the marrow? Because it’s messy. “Fragmenting the bone in an uncontrolled fashion would fill the marrow with bone splinters and it couldn’t be eaten,” Barkai explains. “The chopping tool severs the bone into two neat pieces. It’s an explanation that worked for 2 million years. It was like the Swiss army knife of the Paleolithic.” The resulting marrow might not be totally splinter-free, but it wouldn’t be like trying to swallow a hedgehog.

With the development of the hand ax, hominins had quite the toolkit: the hand ax to butcher the animals, and the “chopping tools” to break their bones for the marrow. “Hand axes were very invested,” Barkai says – referring to the process of knapping. Chopping tools were simpler. Unlike the hand ax, they were not knapped on all edges, and not aesthetically pleasing. Which hand axes are.

Using a chopping tool to break a bone at Tel Aviv UniversityCredit: Ran Barkai
Dr. Flavia Venditti of the University of Tübingen.Credit: Ran Barkai

How did they resolve the mystery bedeviling archaeologists forever: what chopping tools were used for? Reconstructing production techniques, functional studies and residue analysis of organic material left on the rock. In other words, cutting-edge techniques now available to archaeologists. Plus, there were the extraordinary preservation conditions at Revadim, an open-air site on Israel’s Coastal Plain, 40 kilometers (25 miles) southeast of Tel Aviv.

Organic residues can remain on stones for hundreds of thousands of years, other studies have found – if the conditions are appropriate, which they usually aren’t. 

“The specific level [in the archaeological excavation] had been covered in water for a long time, which preserved the organic material. We found a lot of residue,” Barkai says. “The method is significant and so is the specific site – not many sites around the world have such a quality of preservation.”

And what were the organic residues on the chopping tools? Bone, “suggesting they were used mainly for bone-breaking and marrow acquisition,” the team writes.

One implication of this work is that obtaining marrow was important to the early humans – and Barkai argues that it was. The human line can only digest so much lean meat. Beyond a certain level, say 50 percent of caloric intake, we start to suffer from “protein poisoning.”  Our livers can’t handle it.

He has even postulated that the hominins living in another spot in Israel, Qesem Cave, 400,000 to 220,000 years ago preserved the long bones of fallow deer in their cave in order to extract the marrow from them over weeks.

Extracting marrow from a bone broken using a chopping toolCredit: Ran Barkai

Apropos the spare meat, a separate and completely unrelated story postulates (putting it otherwise) that protein poisoning led to domestication of the wolf. How? Because if we hunted an elephant or other megafauna, and we did, we couldn’t possibly finish the whole thing or store surplus properly – so we threw it to the proto-dogs, literally. We shared, and the more amiable of the lupine pack became our first best friends.

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