Dienstag, 4. Dezember 2018

Do Pots and Bones Tell the Same Stories? Research Visit at the University of Bristol – School of Chemistry, November 20-23

A blog post by Sina Lehnig


In order to gain knowledge about the process of food procurement up to certain cooking practices of a cultural group, archaeologists interview the material they recover during their excavations. This includes the analysis of animal bones and plant macro remains, as well as the investigation of certain types of ceramics that were possibly used for transport and the final preparation of food. By doing so they receive information about which animals and plants the inhabitants of a certain region have cultivated or perhaps even imported. However, it is often difficult to assess the actual importance that plants, animals and their products had in people’s everyday lives and diets. The discovery of sheep and goat bones therefore does not yet indicate with certainty whether the animals were kept because of their meat or their secondary products such as milk, cheese and wool. The same applies to cattle, where cows can be used for transport, work, or dairy production. Similar questions arise when it comes to the function of certain vessels in the food preparation process. Due to their shape and characteristics, it is possible to draw conclusions about their use in food storage and preparation, but these conclusions can be regarded as controversial.

In order to get more clarity about the meaning of certain foods and resources in the everyday life of the people who inhabited my research area, the Roman and Byzantine Negev desert, an Organic Residue Analysis (ORA) on ceramics is planned. Since resource exploitation and the acquisition and treatment of food in an arid environment are connected to special challenges (high temperatures, evaporation and low precipitation connected to difficulties for the supply of plants and animals as well as to the storage of food that easily spoils), an analysis that goes beyond the study of bones and plant remains holds additional potential.

Organic residues are often invisible leftovers inside ceramic vessels that come from its original content, from either a single-product use or an accumulation of individual uses. The porous structure of the pottery that can be compared to that of a sponge absorbs organic residues. The most durable and widely occurring among them are lipids. They are the main constitutes of plant and animal cells together with carbohydrates and proteins. Since lipids are hydrophobic they will not readily dissolve in water and therefore survive for long times. The same applies to the durability of the pottery itself: once fired, the material is extremely long-lived. Together, ceramics and lipids form a perfect couple to address archaeological questions regarding diet, resource acquisition/exploitation and vessel use. ORA enables the characterisation of resources including terrestrial animal fats (ruminant and non-ruminant fats, carcass fats and dairy fats can be distinguished), aquatic fats (fish, shellfish, marine mammals), plant oils and waxes, beeswax, as well as resins, tars and bitumens. This information can then be used to clarify whether certain fats only occur in certain vessel forms. Furthermore, they can be compared with the results on animal husbandry and food we have from the archaeozoological analysis.

To evaluate the potential an ORA could have for my research project in the Negev desert, I visited the School of Chemistry at the University of Bristol (Fig. 1) where Prof. Richard Evershed and Dr. Julie Dunne developed a highly regarded laboratory (Fig. 2) for the investigation of organic residues from archaeological sites. I had the chance to see the institution with its technical equipment and to receive an in-depth introduction to the whole method from Prof. Evershed himself. After presenting my research design to both scientists on site, we discussed a possible collaboration. To check the potential of an ORA on ceramic material that comes from the Negev desert, a first survey will be carried out on 60 sherds from the ancient settlement Elusa. I am already looking forward to the results of the study and to comparing them with the data from my other research. This will also show how coherent the picture is that the ORA and archaeozoology draw.
 
Fig.1: Wills Memorial Building at Bristol University (Source: S. Lehnig)

Fig.2: Laboratory at the School of Chemistry where the ORA is carried out (Source: J. Linstädter)

My research stay in Bristol was a great experience and a wonderful opportunity to receive more insight into methods that are a real gain for archaeological research. The contact with the local scientists has shown how important it is that archaeologists and scientists work closely together, network and improve each other’s knowledge about their fields of research.



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