Did Neanderthals use glue? Researchers find evidence of its use in analyzing surprisingly sophisticated 40,000-year-old tools
Neanderthals created stone tools held together by a multi-component adhesive, a team of scientists has found. Their results, which represent the first evidence of a complex adhesive in Europe, suggest that these ancestors of modern humans had higher levels of cognition and cultural development than previously thought.
Researchers from New York University (NYU), the University of Tübingen and the Berlin State Museums were involved in the work, published in the journal Science Advances.
“These amazingly well-preserved tools exhibit a technical solution very similar to examples of tools made by early modern people in Africa, but the exact recipe reflects a Neanderthal ‘turn’, namely 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 from the Department of Ancient Prehistory and Quaternary Ecology at the University of Tübingen and Ewa Dutkiewicz from the Museum of Prehistory and Ancient History of the National Museums in Berlin, re-examined previous finds from the archaeological study Le Moustier site in France, which was at the beginning was discovered in the 20th century.
A stone tool attached to a handle made of liquid bitumen to which 55% ocher has been added. It no longer sticks and is easy to work with. Image courtesy of Patrick Schmidt, University of Tübingen.
The Le Moustier stone tools, which Neanderthals used in the Middle Paleolithic Mousterian 120,000 to 40,000 years ago, are in the collection of the Museum of Prehistory and Ancient History in Berlin and have not previously been studied in detail. During an internal review of the collection, the tools were rediscovered and their scientific value was recognized.
“The objects have been individually packaged and undisturbed since the 1960s,” explains Dutkiewicz. “As a result, the adhering 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, splinters and blades. Ocher is a natural earth pigment; Bitumen is a component of asphalt and can be made from petroleum, but also occurs naturally in the ground.
“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 amounts of ocher are added.”
He and his team examined these materials in tensile tests – to determine strength – and other measurements. “It was different when we used liquid bitumen, which is not really suitable for bonding. Adding 55% ocher creates a malleable mass,” says Schmidt. The mixture was sticky enough to stick to a stone tool without sticking to hands, making it a suitable material for a handle.
Liquid bitumen and ocher pigment before mixing. Image courtesy of Patrick Schmidt, University of Tübingen.
In fact, microscopic examination of the wear of 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: First, 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 light polish distributed over the entire handpiece but not in other parts, which we interpret as the result of abrasion of the ocher due to the movement of the tool in the handle.”
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 development 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 produced by Neanderthals,” concludes Dutkiewicz.
Photomicrographs of wear marks from a tool used by Neanderthals in the Middle Paleolithic. The positions of the micrographs on the artifact are marked in red in the drawing (top left). a) Polishing or shining on the active edge of the tool handle. b) Polishing under paint spots within the area covered by the glue. c) Burr between concave surfaces formed by the removal of pieces of stone that have been naturally torn off and not worn away. d) Dull or worn ridge in the handle area that was covered with glue. Comparison of (c) and (d) shows that the worn part is within the area covered by the intended grip adhesive. Images are displayed in micrometers. Drawing by D. Greinert, Berlin State Museums.
“Our study shows that early Homo sapiens in Africa and Neanderthals in Europe had similar thought patterns,” adds Schmidt. “Their adhesive technologies have equal importance for our understanding of human evolution.”
REFERENCE
Ocher-based composite adhesives at the Moustérien type location document complex findings and high investments
Image: Artist’s illustration of how a Neanderthal might have used an early stone tool, with a handle made from an adhesive mixture of ocher and bitumen. Daniela Greiner, Berlin State Museums, Museum of Prehistory and Early History.