European Neanderthals knew how to cook birch glue (tar) 100,000 years before modern humans arrived on the continent. The sticky material was used in work tools and weapons to join stone to bone and wood. It is waterproof and does not deteriorate for a very long time.

What scientists have learned

The largest amount of Neanderthal glue was found on the territory of Germany. Scientists had two versions of how it was obtained:

• The first assumes that item is simple slid off the rocks after the fire.
• Second, he talks about production “in an industrial way”.

Using a comparative chemical analysis of two samples from Germany and a large collection of birch tar references made using Stone Age techniques, the researchers found that Neanderthals didn’t find birch tar after a fire, but rather did it themselves. Moreover, this did not come easily: they used the most effective method with step-by-step distillation process with restriction of oxygen access during underground heating.

According to the authors, this level of complexity was unlikely to have been invented spontaneously. Technology probably started with simple methods and evolved into a complex process through experimentation.

The researchers dabbled in experimental archeology by recreating five different methods of glue production. They then used infrared spectroscopy, gas chromatography, mass spectrometry and microcomputed tomography to compare their results with artifacts. As it turned out, the presence of oxygen during production leaves a clearly visible trace on the resulting material. Antiquities did not have it, and therefore corresponded to the underground method of production.

Underground techniques are more difficult to perform than surface techniques, as some steps cannot be observed or corrected after the process has begun. This requires more fine-tuning.