An archaeo-metabolomics approach for identifying cedar tar in archaeological samples: differentiating plant products and production processes

The human ability to create manufactured substances is not a modern innovation. It began in the Middle Palaeolithic with the production of birch tar through dry distillation, a process of heating bark under low-oxygen conditions. Over time, this technological knowledge extended to other materials and purposes. Among these, cedar products became especially significant, valued in medicine, technology, cosmetics, and mummification. Yet, distinguishing cedar tar from other cedar products, such as resin or essential oil, has long challenged archaeological science due to their closely related chemical composition. Here we used a GC-MS-based metabolomics approach to identify chemical markers of cedar tar samples. Using modern Cedrus atlantica samples, we defined a set of diagnostic compounds (i.e. dihydro-ar-turmerone, cuparene, dihydrocurcumene, ar-himachalene and 1-methyl-3,5-diisopropylbenzene) that reveal both the cedar origin and the transformative process of dry distillation. As a proof of concept, these chemical markers were searched for and successfully detected in ancient Egyptian mummification balms (664-332 BCE), providing direct evidence for cedar tar use in embalming mixtures and new insights into ancient technologies and cultural practices.