Secrets about invention of Glue

Glue material

Did Neanderthals use glue? Researchers find evidence of its use in the analysis of surprisingly sophisticated 40,000-year-old tools

Neanderthals created stone tools held together by a multi-component adhesive, a team of scientists has discovered. Their findings, which constitute the first evidence of a complex adhesive in Europe, suggest that these ancestors of modern humans had a higher level of cognition and cultural development than previously thought.

Researchers from New York University (NYU), the University of Tübingen and the National Museums of Berlin participated in the work, published in the journal Science Advances.

“These amazingly well-preserved tools show a technical solution very similar to examples of tools made by early modern humans in Africa, but the exact recipe reflects a Neanderthal ‘turn’, which is the production of handles for hand tools,” says Radu. Iovita, associate professor at the Center for the Study of Human Origins at New York University.

The research team, led by Patrick Schmidt of the Ancient Prehistory and Quaternary Ecology section at the University of Tübingen, and Ewa Dutkiewicz of the Museum of Prehistory and Ancient History at the National Museums Berlin, re-examined previous findings from Le Moustier , an archaeological site in France discovered at the beginning of the 20th century.

The Le Moustier stone tools – used by Neanderthals during the Mousterian Middle Paleolithic, between 120,000 and 40,000 years ago – are preserved in the collection of the Museum of Prehistory and Ancient History in Berlin and until now had not been examined in detail. The tools were rediscovered during an internal review of the collection and their scientific value was recognized.

“The objects had been individually wrapped and undisturbed since the 1960s,” explains Dutkiewicz. “As a result, the adhered remains of organic substances were very well preserved.” Researchers discovered traces of a mixture of ocher and bitumen on several stone tools, such as scrapers, flakes and blades. Ocher is a natural earth pigment; Bitumen is a component of asphalt and can be produced from crude oil, but it is also found naturally in soil.

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

He and his team examined these materials in tensile tests – used to determine strength – and other measurements. «It was different when we used liquid bitumen, which is not really suitable for gluing. If 55% ocher is added, a malleable mass is formed,” says Schmidt. The mixture was sticky enough for a stone tool to stick to it, but without sticking to the hands, making it a suitable material for a handle.

In fact, microscopic examination of traces of use on these stone tools revealed that the adhesives on Le Moustier’s tools were used in this way. “The tools showed two types of microscopic wear: one is the typical polishing on sharp edges that usually occurs when working with other materials,” explains Iovita, who carried out this analysis. “The other is a bright polish distributed throughout the presumed handpiece, but not in other parts, which we interpret as the result of abrasion of the ocher due to the movement of the tool within the handle.”

Liquid bitumen and ocher pigment before mixing. Image courtesy of Patrick Schmidt, University of Tübingen.
Liquid bitumen and ocher pigment before mixing. Image courtesy of Patrick Schmidt, University of Tübingen.

The use of adhesives with various components, including various sticky substances such as tree resins and ocher, was already known from the first modern humans, Homo sapiens, in Africa, but not from the first Neanderthals in Europe. Taken together, the development of adhesives and their use in tool making is considered one of the best material evidence of the cultural evolution and cognitive abilities of early humans.

“Composite adhesives are considered one of the first expressions of modern cognitive processes that are still active today,” says Schmidt.

In the Le Moustier region, ocher and bitumen had to be collected from distant locations, which required a lot of effort, planning and a specific approach, the authors note. “Taking into account the general context of the findings, we assume that this adhesive material was manufactured by Neanderthals,” concludes Dutkiewicz.

Micrographs of wear marks from a tool used by Neanderthals during the Middle Paleolithic. The locations of the micrographs on the artifact are indicated in the drawing (top left) in red. a) Polishing, or shine, on the active edge of the tool handle. b) Polishing under dye stains within the area covered by the adhesive. c) Ridge between concave surfaces formed by the removal of pieces of stone that were torn off – rather than worn down – naturally. d) Dull or worn ridge in the grip area that was covered with an adhesive. Comparison of (c) and (d) indicates that the worn part is within the area covered by the designed grip adhesive

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

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