‘Dim-witted’ Neanderthals? They were ‘early engineers’ who produced multi-component glues to handle stone tools

Liquid bitumen and the earth pigment ochre prior to mixing. Credit: Patrick Schmidt

Neanderthals were likely smart engineers. Our predecessors living in France devised their own multi-component glue, not very different from those prepared by modern humans in Africa, according to a new study published in Science Advances.

The glue was used as handles to manipulate several stone tools, such as scrapers, flakes, and blades. It was primarily made up of ochre and bitumen. While ochre is a naturally occurring earth pigment, bitumen is a component of asphalt and can be produced from crude oil, but also occurs naturally in the soil. 

“This is the first such finding of such a compound adhesive (multi-component) made by Neanderthals. There are compound adhesives known from Africa where they date to 60-70 kilo annum (a thousand years),” Patrick Schmidt from the University of Tübingen, told Down To Earth. This is roughly contemporaneous or perhaps a bit older, he added.

The ability to make multi-component adhesives could be the first expressions of the modern cognitive processes that are still active today, Schmidt explained.

One previous study showed that Neanderthals deployed distillation (to separate the components of a liquid mixture through selective evaporation and condensation) to make adhesive handles from birch tar, a sticky substance produced from the bark of birch trees.

In this new study, the Neanderthals produced a new and suitable material by mixing different components. “What this means is that they acted as early engineers creating materials according to their needs,” Schmidt noted.

These findings are based on an analysis of stone tools used by Neanderthals during the Middle Palaeolithic Period between 120,000 and 40,000 years ago. Recovered from Le Moustier, an important archaeological and paleoanthropological site in southwestern France, they are now housed in Berlin’s Museum of Prehistory and Early History.

The tools were rediscovered during an internal review of the collection and their scientific value was recognised. As they were individually wrapped and untouched since the 1960s, the organic substances making up the adhesive were very well preserved, according to the study.

The analysis showed that ochre content in glue was more than 50 per cent, puzzling scientists. This is because bitumen loses its adhesive properties when mixed with large proportions of ochre.

Further analyses revealed that liquid bitumen makes the adhesive malleable when 55 per cent ochre is used. The mixture was just sticky enough to stay glued to the tool but did not adhere to the hands, making it a suitable material as a handle, according to the researchers.

These findings, he added, suggest that early Homo sapiens in Africa and Neanderthals in Europe had similar thought patterns.

Lending more support to this theory is that these materials used in the adhesive were likely sourced from different regions that were far away from each other. This meant that our ancestors made a great deal of effort, planning, and a targeted approach to get them.

The study does not confirm with 100 per cent certainty that Neandertals developed the stone tools. “Neanderthal skeletons of Le Moustier were found at the lower shelter (our artifacts were found at the upper shelter). There are early Homo sapiens incursions in southern France at the same time so scientific rigor requires us to also discuss the possible implications of the pieces in case they were made by Homo sapiens,” Schmidt added.

“Taking into account the overall context of the finds, we assume that this adhesive material was made by Neanderthals,” Ewa Dutkiewicz from the Museum of Prehistory and Early History at the National Museums in Berlin, said in a statement.