Pottery use at the transition to agriculture in the western Mediterranean : evidence from biomolecular and isotopic characterisation of organic residues in Impressed/Cardial Ware vessels

Recent research has attributed the introduction of agriculture in the western Mediterranean to several rapid waves of ‘maritime pioneer colonisation’, followed by indigenous adoption. Impressed/Cardial Wares are thought to have spread simultaneously with domesticates through this region, and are hypothesised to have been used to process domestic plant and animal products. To test this hypothesis, organic residue analysis (ORA) has been applied to 301 Impressed/Cardial Ware vessels recovered from 14 Early and Middle Neolithic sites in the western Mediterranean, to determine their content and function. ORA is a well established technique that can provide direct and sometimes specific evidence of an artefact’s function by analysing lipid residues trapped within its matrix. Characterisation of these fatty residues was carried out using Gas Chromatography (GC), GC-Mass Spectrometry (GC-MS), and GC-combustion-Isotope Ratio MS (GC-c-IRMS). The latter is especially useful, since it allows the δ13C values of two particular fatty acids, C16:0 and C18:0, to be measured. Because of variations in the way these two fatty acids are biosynthesised and routed in different organisms, the difference between their δ13C measurements (i.e. Δ13C values) allow distinction between various types of fat, namely between ruminant and non-ruminant adipose, and ruminant adipose and ruminant dairy products. This research presents the first extensive application of ORA to Early Neolithic pottery recovered from Mediterranean contexts, and was aimed at better understanding the origins of pottery in the Mediterranean and testing their implied association with the transmission of farming from south-west Asia. However, as most ORA studies have been carried out on ceramic assemblages excavated from northern European contexts, the suitability of the method to the Mediterranean region needed to be rigorously tested, in particular since: i) lipid preservation in warmer climates was observed to be considerably lower; ii) shifts in the δ13C and ∆13C isotopic values were identified, compared to UK reference data sets. In view of this, two experiments were set up to: i) determine whether the low chemical fingerprint of plant lipid residues may be a significant contributor to the low lipid yields obtained, which was investigated by re-creating plant residues in ceramic vessels through a series of cooking experiments, and analysing the degraded profile obtained after burial; ii) quantify the shift in the δ13C and ∆13C isotopic signals, by setting up a controlled feeding experiment in the Mediterranean, and comparing the δ13C and ∆13C measurements obtained to northern European values. The results obtained from the experimental work carried out were used to interpret archaeological resides extracted from Impressed/Cardial Ware vessels. Shifts in the δ13C isotopic signals of modern Mediterranean reference fats were identified, and also in the Δ13C values that demarcate the different fat categories. The degraded plant lipid profiles obtained from the cooking experiment were used to identify plant contributions in archaeological residues, and also showed that low quantities of absorbed lipid in archaeological potsherds could potentially indicate a plant input. ORA analysis confirmed the processing of animal and plant products in Impressed/Cardial Wares, and more importantly, unequivocably identified evidence for the use of dairy products in the Mediterranean, dating to the late 7th millennium BC.