Neanderthals Made a Special Glue to Engineer Grips for Stone Tools, Study Suggests

An analysis of forgotten museum artifacts reveals the oldest evidence of a complex adhesive in Europe

An artist's color illustration of a human hand holding a stone tool, with a handle made from ochre and bitumen
An artist's illustration of how a Neanderthal may have used an early stone tool, with a handle made from an adhesive mixture of ocher and bitumen. Daniela Greiner, Staatliche Museen zu Berlin, Museum für Vor- und Frühgeschichte

European Neanderthals were among the first engineers and chemists, producing one of the first types of glue from a mixture of raw materials at least 40,000 years ago, a new analysis finds.

The discovery of this early adhesive in what is now southwest France—consistent with past discoveries of similar substances made by early modern humans in Africa—supports theories that our Neanderthal relatives were more intelligent, adaptive and utilitarian than many give them credit for. Neanderthals, it seems, used the slightly sticky material as a grip for stone tools, according to the study, published in the journal Science Advances last week.

“The fact that Neanderthals made such a substance gives insight into their capabilities and their way of thinking,” Patrick Schmidt, a geologist and archaeologist at the University of Tübingen in Germany and the study’s lead author, tells CNN’s Katie Hunt.

Schmidt and his team discovered the prehistoric glue by paying close attention to something others had overlooked: several stone artifacts, believed to be hunting tools, that were unearthed in 1910 at the French archaeological site Le Moustier. The researchers suggest this site supported Neanderthal life between 40,000 and 120,000 years ago. The neglected artifacts—which had never been studied in detail—had been sitting in the collections of the Museum of Prehistory and Early History in Berlin since the 1960s, individually wrapped.

This quality preservation offered the scientists detailed looks at the early instruments—blades, flakes and scrapers. Five artifacts in particular caught their attention, though, for what still lingered atop them: traces of ocher, an orange-brown earth pigment, and bitumen, a substance that occurs naturally in soil but today is also produced from crude oil.

the front and back of a stone artifact, with traces of an orange substance
One of the stone artifacts found at Le Moustier, with traces of the ocher-bitumen mixture scientists suggest once formed its handle. Gunther Möller, Staatliche Museen zu Berlin, Museum für Vor- und Frühgeschichte

When mixed together, ocher and bitumen create a sticky mass that was likely attached to stones and other tools, the scientists say. Close analysis of the artifacts suggested that, rather than using the adhesive to connect the stone tools to other objects, like wooden handles, they used the substance itself as a handle or grip.

“The tools showed two kinds of microscopic wear: One is the typical polish on the sharp edges that is generally caused by working other materials,” study co-author Radu Iovita, an anthropologist at New York University’s Center for the Study of Human Origins who ran the analysis, says in a statement. “The other is a bright polish distributed all over the presumed hand-held part, which we interpreted as the results of abrasion from the ocher due to movement of the tool within the grip.”

It is also likely that the Neanderthals had to do some experimenting while creating this glue, searching for the right concentrations of ocher and bitumen that stuck just right.

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

The team followed in the Neanderthals’ ways, mixing different amounts of the two substances to find the right combination that would allow them to adhere to a tool, without making their own hands too sticky and impossible to work with. The sweet spot, they found, was a 55 percent ocher, 45 percent liquid bitumen pairing.

Top left: Black sticky bitumen is wrapped around the edge of a blade. Left: Gloved hands wrap the bitumen around a blade. Right: A gloved hand holds a handle made from bitumen and ochre, with a sharp blade affixed to it, like a knife, seen bottom right.
Left: The researchers recreate a Neanderthal tool by wrapping sticky bitumen on a sharp blade. Right: Ocher is added, creating a handle that adheres to the blade but isn't too sticky, so that human hands can still hold and use it. Schmidt et al., Science Advances (2024)

Adhesives have been found at different archeological sites around Europe, says Marie-Hélène Moncel, a research director at the French National Museum of Natural History who was not involved in the study, to CNN. And in Africa, tree resin and ocher had been used to create similar compounds in ancient communities.

Based on the context of the newly examined artifacts, including their age of roughly 40,000 to 60,000 years, the team concluded they were made by Neanderthals, rather than modern humans. This glue is one of the oldest and most complex to be discovered on the European continent.

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

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