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UJ, Leiden researchers discover how Neanderthals made the first glue

Neanderthals made glue from birch bark tar to haft knives and spears as early as 200 thousand years ago. But how did they make glue from bark and it is really as difficult as generally assumed? Archaeologists from the University of Johannesburg and Leiden University set out to test this and found that there are quite simple methods to make birch bark tar.

In a recently published experimental study, archaeologists from the University of Johannesburg (UJ) together with Leiden University in Netherlands, demonstrated three ways Neanderthals may have made the world’s oldest known adhesive. Until now, it was assumed that the distillation of birch bark into tar was a complex technological feat. This was partly because scientists themselves were unable to make viable amounts of tar using Neanderthal technology, and because lab studies suggested the temperature had to be kept precisely between 340 and 370 degrees Celsius.

Two-hundred-thousand-year-old tar lumps found at an archaeological site in Italy are considered to be the first evidence of transformative technology. According to Geeske Langejans, Project Leader and Senior Research Associate, University of Johannesburg, “This means that there is a complete transformation of materials. A familiar example of such a technology is baking a cake. Once you have baked a cake, you can no longer separate it back into eggs, flour, butter, and sugar. So the end product is completely different from the original ingredients, in our case birch bark and fire. However, adhesives from such a remote time period are incredibly rare and there is no direct archaeological evidence on how they were made.’’

In this study, the archeologists Kozowyk, Soressi, Pomstra and Langejans used only Stone Age technology and materials to better understand the Neanderthal invention. Langejans says, “We have used the present to understand the past.”

To make an adhesive, birch bark is heated in the absence of oxygen and is transformed into a sticky black tar. If oxygen is present, the tar burns away. The findings show that there are multiple ways of manufacturing birch bark tar. Some methods are very straightforward, requiring little more than a roll of birch bark and hot embers. Other methods are more complex and include containers, pits, and small earthen structures.

The authors concluded that Neanderthals likely invented tar by recombining know-how and materials they already had. This process would have begun with a simple method using only birch bark and embers, and may have later evolved to more complex processes using an earthen mound.

Paul Kozowyk, first author of the paper, adds, “We found that there’s more than one way to make tar, and that each method was successful despite the large temperature variations we recorded, between 300 and 600 degrees Celsius. This means that the control of fire did not have to be as precise as previously thought.”

“This work is greatly inspired by my collaboration with professor Marlize Lombard, Director of the Centre for Anthropological Research at the University of Johannesburg. For many years we studied the requirements of Stone Age technologies, crucial in our understanding of the evolution of early human intelligence,” said Langejans.The authors show that tar production does not have to be complicated, but what does this mean for the Neanderthals? “To make as much tar as was found in Italy, you need to repeat the simplest method 30 times or use the more complicated earthen mound method that has a higher yield. It is likely that Neanderthals used a range of methods, a simple method for the quick maintenance of a spear, and a higher yield method for a major service,” explained Langejans.

The study confirms that it was indeed possible for Neanderthals to transform birch bark into tar with the materials and technology already in use at the time. Considering that the first evidence for tar production is more than 200 thousand years old and was found in Europe, it is likely that Neanderthals were one of the first hominins to use fire to produce adhesives.


Glue Img
Dripping Glue. Photo credit: P.Kozowyk
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