Birch Bark Tar Production: Experimental and Biomolecular Approaches to the Study of a Common and Widely Used Prehistoric Adhesive

Abstract

Birch bark tar, the oldest adhesive known in Europe, was widely used during Prehistory. This material, produced by the dry distillation of birch bark, has been identified in various spheres of activities and provides valuable information on the know-how and technical and territorial systems of past societies. This biomaterial can also provide evidence on socio-economic networks and mobility. However, very little is known about the production systems of birch bark tar during Prehistory, including the Neolithic period. The lack of findings in the archaeological record necessitates the development of an approach that combines experimental archaeology and biomolecular chemistry. We present here (1) the results of experiments in which different birch bark tar production systems were tested and (2) the molecular signatures of the birch bark tars produced according to different processes based on the use of ceramic vessels. The key role of bark quality is highlighted for the first time. This study also details direct archaeological inference of the experimental results obtained: a total of 23 samples from the site of Nice-Giribaldi (France, second part of the fifth century BCE) was investigated. Different categories of birch bark tars were identified during Neolithic in the south of France, providing evidence for the existence of complex manufacturing systems and procurement networks.

Birch tar production does not prove Neanderthal behavioral complexity

“…This has been the case of the 2 oldest GC-MS-analyzed examples of birch tar from Campitello and Königsaue (24,25). Analyzing our own experimental tar, we also identified both biomarkers (betulin and lupeol) in addition to 3 degraded markers (lupa-2,20 [29]-diene, α-betuline I, and lupa-2,20 [29]-dien-28-ol) that have been described to indicate heat treatment in previous experimental studies (22) and that were found in archaeological tar samples (26). Thus, tar produced in oxygenized environments with our experimental setup provides a molecular signature of birch bark tar.…”

“…2D). Sample extraction and analytical conditions were performed following protocols established for birch tar analysis (22). GC-MS has previously been used to identify Paleolithic tar as being birch bark tar through the presence of characteristic pentacyclic triterpenes, in particular, betulin and lupeol (23), and their degradation markers that may indicate heat treatment (e.g., lupa-2,20 [29] diene, lupa-2,20 [29]-dien-28-ol, and allobetul-2-en).…”

Birch-bark tar in the Roman world: the persistence of an ancient craft tradition?

“…These categories of molecular biomarkers were recently defined by a programme of experimental archaeology by Rageot et al . (2019). Some of them, such as lupa-2,20(29)-dien, lupa-2,20(29)-dien-28-ol and betulone, may also result from natural decay.…”

Leftovers: The presence of manufacture‐derived aquatic lipids in Alaskan pottery

“…; Rageot et al . ). Other substances identified through residue analysis are more ambiguous to interpret, and so far there has been little consideration about whether fats, oils and waxes used in the manufacture of pottery leave a significant residue signal following firing.…”

“…The study of lipid residues in archaeological pottery has advanced significantly over the past decade and it has yielded new information about the prehistoric diet and cuisine (Craig et al 2013;Lucquin et al 2016b;Gibbs et al 2017). Various lipid compounds, such as tars, resins and waxes, have also been identified which were clearly used to repair pottery and to waterproof porous vessels, and had nothing to do with food preparation or cuisine (Regert et al 2003;Regert 2004;Hjulström et al 2006;Reber and Hart 2008;Stern et al 2008;Rageot et al 2019). Other substances identified through residue analysis are more ambiguous to interpret, and so far there has been little consideration about whether fats, oils and waxes used in the manufacture of pottery leave a significant residue signal following firing.…”