In 2005, archaeologists came across the oldest-known evidence of hafting—adhering a stone blade to a wood or bone handle—in a quarry in central Italy. The finding suggested something exciting: that Neanderthals had come up with a way to produce birch tar.
Creating sticky tar or resin was believed to be a pretty sophisticated process. In a 2017 paper, experimental archaeologists attempted to make tar using the tools Neanderthals would have had at their disposal. They experimented with three methods, all of which required control of fire, a low-oxygen environment and a little ingenuity, that produced usable quantities of tar.
The discovery that Neanderthals could make tar played into an argument that researchers have been having over the last decade about whether Neanderthal intelligence was more or less on par with Homo sapiens. But a new study found a much simpler way to produce birch tar, suggesting glue isn't a good proxy for Neanderthal smarts.
In the latest paper, published in the Proceedings of the National Academy of Sciences, researchers tried to make the tar using the simplest method possible. They collected live and dead birch bark in the forest then burned the bark near flat river stones. When the bark burned down in about three hours, it left a sticky resin that was similar to the kind found in Neanderthal sites, which could be scraped off and used as an adhesive.
After making the resin, the team then constructed a wood scraping tool with the resin. They then used a small robot to drag the tool over a piece of wood for 170 strokes. After all that wear and tear, the resin showed no sign of weakening; in fact, it had more sticking power than the resin made from the low-oxygen experiments.
“Our paper challenges common beliefs that the presence of birch tar in Neanderthal archaeological assemblages means they had sophisticated cognitive abilities,” says co-author Radu Iovita of New York University.
But Paul Kozowyk of the University of Leiden, first author of the 2017 paper, is pushing back against those conclusions. Even if Neanderthals were using the simpler method, he tells Ruth Schuster at Haaretz, their use of the resin still indicates a level of planning and complex thinking. “I would suspect that to make the quantities of tar found at sites like Campitello and Konigsaue, Neanderthals already had a more efficient way of making tar,” he says. “Further, the idea more than 200,000 years ago to recognize this sticky substance, to figure out how it got there, and then to repeat the process for hours to make enough tar to collect and glue a multi-component tool together, still shows remarkable determination and forethought by Neanderthals!”
Another study published in June in PLOS One found that Neanderthals in two caves in Italy were traveling to nearby pine forests and collecting sap to process into an adhesive as well. Because pine sap hardens when exposed to the air, it has to be warmed over a fire to be turned into a liquid adhesive. “This is one of several proofs that strongly indicate that Neanderthals were capable of making fire whenever they needed it,” says co-author Paola Villa of the University of Colorado, Boulder.
All of which is to say that regardless of their ability to control fire or how complex their glue-making skills were, the emerging picture of Neanderthals is still much different, and much more human, than previously thought.