Contents of pottery vessels from the megalithic tomb of Zambujeiro, Portugal

Organic residue analysis applied to the archaeological materials relies on the advances in chromatographic and mass spectrometric techniques. Chemical analysis can help to uncover the original contents of the vessels and past pottery use. Organic molecules can preserve well inside the porous structure of the ceramic, thus the information obtained can be used to identify the presence of natural products or food remains.

The Great Dolmen of Zambujeiro, is an archaeological site located on the left bank of Ribeira de Valverde stream, near the village of Valverde, in the municipality of Évora. It is the largest chambered megalithic tomb in Alentejo region of Portugal, constructed between the 4^th and mid-3^rd millennia BC. Multiple burials were accompanied by various goods, including amber beads, chert arrowheads, and remains of pottery vessels. Organic residue analysis of 27 selected ceramic sherds from 24 distinct vessels was performed using gas chromatography coupled with mass spectrometry (GC-MS).

The analysis revealed organic content in all analyzed vessels, in a good preservation state, as unsaturated fatty acids and monoacylglycerols (MAGs) were detected in most samples. Remains of fats and oils were recognized by the distribution of saturated and unsaturated fatty acids, dicarboxylic acids, and fatty alcohols. Furthermore, in several vessels of different forms, residues of degraded beeswax were recognized by a characteristic chemical profile. These results give an insight into funerary practices and provide direct evidence for the exploitation of bee products at the time Zambujeiro was used as a burial site.

Acknowledgements: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement N.º 766311. The authors thank the Portuguese Foundation for Science and Technology (FCT) for funding Ana Manhita’s individual scientific employment contract nr. CEECIND/00791/2017.