The aceramic production of <Emphasis Type="Italic">Betula pubescens</Emphasis> (downy birch) bark tar using simple raised structures. A viable Neanderthal technique?

Following on from our previous research into the prehistoric aceramic distillation and production of birch bark tar, this series of exploratory experiments investigated the use of raised structures within a fire. These field-based experiments were conducted using sand, gravel, wood fuel, and bark from Betula pubescens (downy birch). The structures that were created were simple raised sand mounds, which reflected known Neanderthal combustion surfaces from the Middle Palaeolithic. The bulk of the experiments were recorded throughout using a thermocouple to provide temperature readings from the base of the bark pyrolysis chamber. The experiments proved successful at producing birch bark tar and several containers were used to catch the tar for later analysis. Based on the results, the authors contend that not only could Neanderthals control fire but that regular birch bark tar production by Neanderthals was most likely a result of specific chaînes opératoires in order to provide the necessary control and outcomes.     

Experimental explorations into the aceramic dry distillation of <Emphasis Type="Italic">Betula pubescens</Emphasis> (downy birch) bark tar

A range of experiments were conducted in an attempt to create tar from the bark of Betula pubescens (downy birch) using an aceramic dry distillation process. Fire structures based on small pits and small kiln-like mounds were explored with a focus on fire intensities and differing burn times under field-based conditions. Heat penetration presented itself as an all-important factor, and the depth of the construction of the structures and features was considered to directly correlate to the impact of the heat. Single variable experiments confirmed that the necessary reducing atmosphere was achievable despite friable soil, but that heat would not penetrate a 50- to 80-mm-deep layer of grass turf. The evolution of structures from pits towards a raised type resulted in kiln-like structures which proved more successful. Though the experiments did not successfully produce tar as a finished product, they did lead to a better understanding of the dry distillation process of the established technology of birch bark tar extraction in aceramic societies.