Neanderthals already made glue from birch tar 200 thousand years ago, but how? Archaeologists have shown that Neanderthals could extract useful amounts of tar from the bark of birch trees. Even if they messed around a bit…
We already knew that Neanderthals could make tar. But archaeologists thought that they used technically very complicated methods whereby they had to keep the temperature between three hundred and forty and three hundred and seventy degrees Celsius. Research by Leiden archaeologists Paul Kozowyk and Geeske Langejans has now shown that strict temperature control is not necessary at all to bring production to an acceptable level of usability. And that's new.
Good fitting connection
What did ancient Stone Age people use birch tar for? The stuff turned out to be an important improvement to stick a spearhead to a spear, for example. Compared to previous technology using animal tendon, it was easier to make a well-fitting connection with tar. By smearing the birch tar on it, the arrowhead was stuck. Axes and other chopping and scraping tools, in which wood was connected to stone or bone, also received a quality impulse through the use of tar.
Paul Kozowyk:“You shouldn't think that two hundred millennia ago 'someone' suddenly had a bright idea:you know what, we're going to do it like this from now on. No, several aspects of tool assembly were seen not working properly. Birches were available in abundance:generally good firewood and the bark is beautiful tinder.”
“The birch bark rolls up on its own as soon as you pull it off the tree. Between those rolled-up layers of bark, droplets of adhesive material were seen forming in the fire, which they then used for adhesive work. Gradually, the need for constant availability of such material arose. It takes many tens of thousands of years.”
Rare glue
Featured by the editors
MedicineWhat are the microplastics doing in my sunscreen?!
AstronomySun, sea and science
BiologyExpedition to melting land
At an archaeological site in Campitello, Italy, just south of Florence, remains of two hundred thousand year old tar glues have been found. That find is considered evidence for one of the first "transformation technologies" acquired by the earliest humans. These types of technologies involve a complete transformation of the ingredients; think, for example, of baking a cake, where the baking can never change back to eggs, butter, flour and sugar. By manipulating birch bark in such a specific way, an entirely new material was created.
Preserved glues from such a distant period of time are extremely rare – there is only one site left besides Campitello with chemically identified macroscopic amounts of glue residues across Europe, Königsaue in Germany – and direct archaeological evidence is lacking for how it was made.
Geeske Langejans:“In such situations, experimental archeology opens a window to Neanderthal technology. Our Neanderthal relatives from the Old Stone Age heated birch bark without oxygen to prevent combustion, after which a sticky black tar was formed. In this experimental study we only used materials and techniques that were also available in the Stone Age to better understand the invention:birch bark and fire. We also used common sense about what Neanderthals might have done.”
Not accurate
Previous attempts by other researchers to experimentally make birch tar using aceramic technology (that is, without pottery) yielded only small amounts of tar residue, or something else went wrong. It has subsequently been assumed that this tar production must have been very difficult, especially in terms of temperature control.
Paul Kozowyk:“We have shown that there is more than one way to make tar, and that a large temperature variation was possible for each method. In a nutshell:tar is produced at three hundred degrees Celsius, but also at six hundred. This means that Neanderthals did not have to operate as accurately as previously thought.”
Copy
In an experimental setting in Zeewolde, in a replica of the house of the first Dutch farmers, researchers Kozowyk and Langejans used all kinds of baking, roasting and collecting techniques to see what worked best. They weighed and measured all variables, for example the kilos of firewood, the temperature of the fire and of the birch bark, the amount of birch bark and the local wind speed.
Several methods were found to work. Some are quite simple, using little more than a roll of birch bark and a few glowing bits of charcoal. Other methods are more complex, involving containers, dug pits and small earth kilns.
Langejans:“It is not inconceivable that the Neanderthal, when he carried out major repairs to his armor and tools, used a different method than when he had to quickly repair a few spears while on the hunt. The more complicated the method, the higher the yield, but our main finding is that temperature is not a show stopper. Clever control of heat was apparently unnecessary.”