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, 116 (36), 17707-17711

Birch Tar Production Does Not Prove Neanderthal Behavioral Complexity


Birch Tar Production Does Not Prove Neanderthal Behavioral Complexity

Patrick Schmidt et al. Proc Natl Acad Sci U S A.


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.

Keywords: Neanderthal birch tar; adhesives; cognitive complexity; early pyrotechnology; modern behaviors.

Conflict of interest statement

The authors declare no conflict of interest.


Fig. 1.
Fig. 1.
Experimental birch tar making with the condensation technique. (A) Schematic drawing of the experimental setup: a cobble (1) with an inclined surface overhanging a piece of birch bark (2) is used as support for the condensation of birch tar directly above the burning bark (3). (B) Photo taken during experimentation using the setup shown in A. (C) Photo of the cobble surface where tar can be scraped off and the stone tool used for scraping. (D) Photo of a 0.62-g piece of tar produced in a single 3-h session (including bark collection).
Fig. 2.
Fig. 2.
Analysis of birch tar produced by the condensation technique. (A) experimental setup using the robot arm for wood scraping under controlled conditions. (B) Actualistic defleshing experiment using the same hafted tool as in A. (C) Three photos taken of a single sample at different moments during a lap shear test, (Left) 93.3 MPa before plastic deformation of the tar; (Middle) 90.7 MPa at the beginning of plastic deformation; and (Right) after failure of the tar. (D) Chromatogram of tar produced with the condensation technique showing biomarkers and markers of heat treatment: 1 = lupa-2,20 (29)-diene; 2 = α-betuline I; 3 = lupa-2,20 (29)-dien-28-ol; 4 = lupeol; 5 = betulin. RT, retention time.

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