Everyday materials

The researchers experimented instead with ordinary materials which were around in the Stone Age. They collected cut fresh birch bark or collected dead bark in the forest and burned it near flat river stones. After three hours, the process yielded a usable amount of a black sticky material. The tar could easily be scraped off the surface of the stones. “The tar had similar molecular characteristics to archaeological samples we have from Neanderthal sites. More importantly, it formed a stronger glue than tar produced in more complex oxygen-free processes," says Schmidt.

In order to test its adhesive strength, the researchers used the pitch to stick a stone scraper to a wooden handle; they were able to use it to scrape the tough outer membrane from the thigh bone of a calf. "The adhesive effect did not wear off," said the co-author of the study, Matthias Blessing from the Tübingen research team. The researchers say this method of making birch tar is so simple that early humans could have easily discovered it by accident in the course of their everyday activities. All that was needed was a fire and birch bark over a smooth surface of stones or bones. “It may be that this knowledge was not passed on directly, but that adhesive effect of the birch residues was re-discovered several times,” Claudio Tennie speculates.

The production and use of birch pitch can therefore no longer serve as an indicator of modern or complex behavior. “This takes away one key argument in the ongoing debate over the cognitive and cultural abilities of Neanderthals. The fact that they may already have been highly developed must be proven in other ways,” Schmidt says.

Publication:

Patrick Schmidt; Matthias Blessing; Maxime Rageot; Radu Iovita; Johannes Pfleging; Klaus G. Nickel; Ludovic Righetti; Claudio Tennie: Birch tar extraction does not prove Neanderthal behavioral complexity. PNAS – Proceedings of the National Academy of Sciences, August 19, 2019; dx.doi.org/10.1073/pnas.1911137116