Adhesive Grips on Neanderthal Tools Reveals Species’ Advanced Creativity

A team of researchers from Germany and the United States recently published a study that suggests Neanderthals might have had far more creative intelligence than previously believed.

The study, published in the journal Science Advances involved an examination of a set of stone tools made by Neanderthals during the Middle Paleolithic period, or somewhere between 120,000 and 40,000 years ago. These tools were coated with a complex adhesive substance that would have made them easier to grip and maneuver, demonstrating that Neanderthals had the advanced cognitive capacities necessary to manufacture such a substance, and to figure out what to do with it to make their lives better.

Despite the immense passage of time, traces of the adhesive were found on several different tools, which were recovered from an archaeological site in France known as Le Moustier in 1910. The toolmaking industry from which these artifacts came has been labeled Mousterian, to highlight the historical significance of the finds at this Middle Paleolithic Neanderthal site.

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A Handle Made from Glue? Only a Neanderthal Would Think of That

The stone tools from Le Moustier had long been held in storage at the Berlin Museum of Prehistory and Early History. But amazingly, they had never been analyzed in detail.

This oversight was finally rectified by a team of researchers led by Patrick Schmidt from the University of Tübingen’s Early Prehistory and Quaternary Ecology section, Ewa Dutkiewicz from the National Museums in Berlin, and Radu Iovita from New York University’s Center for the Study of Human Origins, who learned about the existence of the long-forgotten tools following a routine inventory undertaken by museum staff.

After gaining possession of the tools from the museum, the researchers carefully examined their surfaces, searching for marks of wear and any other signs that might reveal how the tools were used or manufactured. Needless to say, they were delighted to discover traces of a sticky adhesive still attached to their tool faces in certain spots. Fortunately the tools had been kept safely wrapped for the past 60 years, which guaranteed the adhesive wouldn’t dissolve into dust.

“These astonishingly well-preserved tools showcase a technical solution broadly similar to examples of tools made by early modern humans in Africa, but the exact recipe reflects a Neanderthal ‘spin,’ which is the production of grips for handheld tools,” Radu Iovita said, in a New York University press release.

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Stone artifact from the upper rock overhang of the Neanderthal site Le Moustier with remains of the bitumen-ocher mixture from which the handle was made. (© State Museums in Berlin, Museum of Prehistory and Early History / Gunther Möller)

Neanderthal Innovation

What Iovita is revealing here is that the adhesive found clinging to these tools was not used to attach handles, but had itself been shaped and molded to create such handles.

After completing their chemical analysis of the sticky substance, the researchers were not surprised to find that bitumen was one of its primary ingredients. This naturally occurring pitch is derived from petroleum and has been used to make glues since ancient times. But while the bitumen was expected, the researchers were puzzled by the presence of high levels of ochre, an earth pigment that is not nearly as sticky as bitumen.

“We were surprised that the ochre content was more than 50 percent,” Schmidt explained. “This is because air-dried bitumen can be used unaltered as an adhesive, but loses its adhesive properties when such large proportions of ochre are added.” 

As it turns out, this was the reason why the ochre was added to the adhesive in the first place. The researchers eventually realized that an ochre-heavy bitumen mixture would have produced a strong compound that would stick to the surface of a stone tool quite firmly, but would not stick to human (or Neanderthal) skin because it contained so much ochre.

A stone tool glued into a handle made of liquid bitumen with the addition of 55 percent ochre. It is no longer sticky and can be handled easily. (Image courtesy of Patrick Schmidt, University of Tübingen)

This meant a large glob or clump of the flexible adhesive could be pressed onto the outside of a scraper, chopping tool or cutting blade, and then shaped into a grip that would allow that tool to be firmly held and controlled by its user. The bitumen/ochre handle would not come loose, nor would it stick to the skin of the individual wielding the tool. In other words, the compound adhesive featured the perfect combination of characteristics to function as a strong and reliable handle.

This conclusion is based on more than just logical supposition. The researchers examined the surfaces of the Mousterian stone tools and found evidence to support this idea.

“The tools showed two kinds of microscopic wear,” Iovita stated. “One is the typical polish on the sharp edges that is generally caused by working other materials. The other is a bright polish distributed all over the presumed hand-held part, but not elsewhere, which we interpreted as the results of abrasion from the ochre due to movement of the tool within the grip.”

More Surprises from the Surprisingly Brilliant Neanderthals

The development of such an ingenious solution based on complex chemistry implies advanced creative intelligence, expressed in the realms of ancient science and engineering.

Scientists have never been certain that Neanderthals possessed this kind of intelligence. But what the German and American researchers have discovered represents the oldest known sample of a complex adhesive found anywhere in the world, and it is linked to a toolmaking culture and archaeological site closely associated with the Neanderthals in the Middle Paleolithic period. 

It is known that early modern humans living in Africa created high-quality adhesives from multiple compounds, including sticky substances such as bitumen, tree resins and ochre. But the discovery that Neanderthals were making these glues even earlier was quite a revelation.

“Compound adhesives are considered to be among the first expressions of the modern cognitive processes that are still active today,” Schmidt noted.

The fact that Neanderthals were making such adhesives and putting them to such good practical use is the latest evidence that shows Neanderthals were not primitive or simple-minded, but shared an impressive cognitive legacy with their Homo sapiens cousins.

“What our study shows is that early Homo sapiens in Africa and Neanderthals in Europe had similar thought patterns,” Schmidt said. “Their adhesive technologies have the same significance for our understanding of human evolution.”

Top image: Reconstruction of how the stone artifact with the handle made of the bitumen-ocher mixture could be held by a Neanderthal woman.             Source: © Berlin State Museums, Museum of Prehistory and Early History, illustration: Daniela Greinert

By Nathan Falde