Neanderthals and other early humans produced a tarry glue from birch bark; this was long considered proof of a high level of cognitive and cultural development. Researchers had long believed that birch tar—used by the Neanderthals to make tools—could only be created through a complex process in which the bark had to be heated in the absence of air.
However, an international team led by researchers at the University of Tübingen and including faculty from New York University's Department of Anthropology and the NYU Tandon School of Engineering found that there is a very simple way to make this useful glue.
The study was published August 19 in Proceedings of the National Academy of Sciences (PNAS).
Patrick Schmidt et al. Birch tar production does not prove Neanderthal behavioral complexity, Proceedings of the National Academy of Sciences (2019).
Significance: We found a previously unknown way to produce birch tar. Instead of creating cognitively demanding structures (underground or in containers), this method consists of simply burning bark close to cobbles in a hearth. The tar is deposited on the stones and can be scraped off for use. This approach to interpreting early tar resolves the mystery of the associated and still not understood early technical complexity and provides a “discoverable” pathway to one of the earliest pyrotechnologies. These results have implications for our interpretation of birch tar in the archaeological record: Birch tar from early archaeological contexts alone can no longer indicate the presence of modern cognition and/or cultural behaviors in Neanderthals.
Abstract: Birch tar production by Neanderthals—used for hafting tools—has been interpreted as one of the earliest manifestations of modern cultural behavior. This is because birch tar production per se was assumed to require a cognitively demanding setup, in which birch bark is heated in anaerobic conditions, a setup whose inherent complexity was thought to require modern levels of cognition and cultural transmission. Here we demonstrate that recognizable amounts of birch tar were likely a relatively frequent byproduct of burning birch bark (a natural tinder) under common, i.e., aerobic, conditions. We show that when birch bark burns close to a vertical to subvertical hard surface, such as an adjacent stone, birch tar is naturally deposited and can be easily scraped off the surface. The burning of birch bark near suitable surfaces provides useable quantities of birch tar in a single work session (3 h; including birch bark procurement). Chemical analysis of the resulting tar showed typical markers present in archaeological tar. Mechanical tests verify the tar’s suitability for hafting and for hafted tools use. Given that similarly sized stones as in our experiment are frequently found in archaeological contexts associated with Neanderthals, the cognitively undemanding connection between burning birch bark and the production of birch tar would have been readily discoverable multiple times. Thus, the presence of birch tar alone cannot indicate the presence of modern cognition and/or cultural behaviors in Neanderthals.