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.

Plant resins, tars and organic fossil substances provide valuable insights into the ecological, environmental and cultural contexts of ancient societies. Their study offers evidence of past knowhow, production systems, socio-economic networks and mobility. In this paper, we present new data from 16 sites located in the North-West Mediterranean that provide new insights into the exploitation of these substances for their adhesive and hydrophobic properties throughout the Neolithic (6000-2500 cal BCE). The substances investigated are discussed in the light of their molecular composition, their uses and manufacturing processes. Spatial analyses were also performed to elucidate raw material procurement strategies. This study considerably increases the body of data available from the Mediterranean and tells a diachronic story of adhesive production and use throughout the Neolithic, highlighting the variability and complexity of production systems and supply networks at different spatial scales. While most adhesive and hydrophobic substances were probably collected locally, birch bark tar was very likely transported across long distances to reach Mediterranean coastal sites. Birch bark tar exploitation intensified in South-Eastern France during the Middle Neolithic, while the Late Neolithic is characterised by a diversification of the substances employed and their range of uses: bitumen, birch bark tar (pure or mixed with Pinaceae resin, beeswax and possibly fat/oil) were important materials that were used for a variety of purposes. Pure Pinaceae exudates were exclusively employed for waterproofing pottery. We also highlight the standardisation of birch bark tar production for adhesive manufacture observed in Provence during the first part of the 4 th millennium cal. BCE.

Post-firing treatments, produced by the interaction of an organic material with the hot surface of a ceramic, are frequently described in ethnographic literature, but have rarely been identified in archaeological ceramic assemblages. In order to address this question, this paper describes a methodology that combines macro-and microscopic observation and molecular analysis. The study of experimental ceramic vessels provided diagnostic tools to identify the type of substances, their liquid or solid state, and their mode of application and attested that the post-firing treatments do not completely waterproof the ceramics. The difficulty to observe macro-and microscopic evidence of post-firing treatments when pots are fired in reducing atmosphere suggests that these processes are probably underestimated in archaeological assemblages. Furthermore, the identification of molecular thermal transformation markers, such as ketones, calls into question their classical interpretation as markers for the cooking of fatty content. This pioneering work highlights the complexity of studying post-firing treatments, which leave small traces that are easily missed or misinterpreted. In order to address this issue, we propose a multi-analytical approach, which can serve as a basis for future studies to explore the full diversity of post-firing treatments mentioned in ethnoarchaeological literature.