40,000-year-old glue suggests Neanderthals were smarter than we thought

A type of complex glue found on stone tools made by Neanderthals has given researchers new insights into the intelligence of this extinct human species. Made from a mix of bitumen and ochre, the multi-layer adhesive resembles the glue used in the past Homo sapiens in Africa, indicating that our ancient cousins ​​may have had a similar level of knowledge as our own ancestors.

It is known that Neanderthals, like early modern humans, used birch pitch as a kind of glue to attach stone knives to wooden handles. Until now, however, more refined mixtures containing ocher were only attributed to our own species.

Yet this story has emerged thanks to a new analysis of 40,000-year-old stone tools from the iconic Le Moustier site in France, which lends its name to the Mousterian technological complex largely associated with the Neanderthals of the Middle Paleolithic. Chemical analyzes of colorful residues on five Neanderthal-made tools revealed traces of both goethite toker and bitumen, a component of crude oil.

Neanderthal glue

Traces of the old glue on a stone artifact.

Image credits: Staatliche Museen zu Berlin, Museum für Vor- und Frühgeschichte, photo: Ewa Dutkiewicz

“We were surprised that the ocher content was more than 50 percent,” study author Patrick Schmidt explained in a statement. “This is because air-dried bitumen can be used unchanged as an adhesive, but loses its adhesion properties when such large amounts of ocher are added.”

The researchers therefore concluded that the mixture was not suitable for hafting, but may have had another function. Among Africans, for example Homo sapiensAdhesives containing ocher were sometimes used as a grip for stone tools, eliminating the need for a handle and acting as a direct point of contact between the utensil and the user’s hand.

To investigate how this particular mixture may have been used by the Neanderthals of Le Moustier, the study authors conducted their own experiments using stone tools and different formulations of ancient glues. When using handles made of pure bitumen, they found that the substance left “sticky marks on the hand, which are difficult to remove.”

However, mixtures containing 55 percent goethie toker “feel firmer and do not feel sticky.”

“When using such a grip, no bitumen sticks to the manipulator’s hands,” the researchers write. “Mixing high ocher amounts into fresh bitumen therefore offers an advantage for such composite tools.”

Neanderthal glue

Pure bitumen is too sticky, but the addition of ocher ensures a good grip.

Image credit: Schmidt et al., Sci. Given 10, eadl0822 (2024)

Based on these findings, the study authors conclude that Neanderthals used the mixture because it was sticky enough to increase their grip on a stone tool, but not so sticky that it stuck to their hands. This made it the perfect material to use as a grip.

“These astonishingly well-preserved tools demonstrate a technical solution broadly similar to examples of tools made by early modern humans in Africa, but the exact recipe reflects a Neanderthal ‘twist’, namely the production of handles for portable tools,” said the author of the research. Radu Iovita.

Such innovation becomes even more impressive when you consider that the nearest source of bitumen to Le Moustier was an oil field some 200 kilometers (124 mi) to the south, while ocher would have been collected from a goethite outcrop about 50 kilometers (31 miles) to the north. from the old site.

According to the study authors, putting these two ingredients together for a specific purpose “involved cognitive processes, such as future planning and imagination.”

“Composite adhesives are considered one of the first expressions of modern cognitive processes that are still active today,” Schmidt said. “What our research shows is so early Homo sapiens in Africa and Neanderthals in Europe had similar thinking patterns.”

The study was published in the journal Science Advances.

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