New study provides first visualisation of ancient lipids trapped in archaeological pottery
16 June 2020
A new study led by former Bristol Postdoctoral Research Associate Dr. Simon Hammann, which provides the direct visualization of ancient fats and oils preserved in the walls of archaeological pottery vessels, has just been published in Proceedings of the National Academy of Sciences USA.
Analysis of ancient organic residues absorbed and preserved in the fabric of archaeological pottery has, by now, been used to identify the original contents of thousands of pots dating back many millennia. This has led to discoveries including the use of dairy products by early prehistoric farmers, and to illuminate the particular uses of certain styles of prehistoric, and later, pottery.
However, to this day it was not fully known how these residues actually came to be present in the ceramic matrix, and how they were then preserved over archaeological timescales. In this study, the team from the Universities of Bristol and Nottingham used a non-destructive technique called Secondary Ion Mass Spectrometry (SIMS) to visualize and map the distribution patterns of fat and oil (lipid) molecules within the walls of archaeological ceramics with sub-micrometer precision.
Using this method, the team was able to show that, contrary to the previously established theory that lipids were predominantly trapped in small, micrometer-sized pores, lipids were actually also held in more macroscopic structures, in clearly defined zones of up to 400 µm in size. Furthermore, the findings suggested that a reaction of lipid molecules with calcium carbonate inclusions in the pots led to compounds becoming practically insoluble in water, which would explain the poor extractability of these compounds with some commonly used methods.
This new method of spatially-resolved analysis of lipids in archaeological samples offers completely new opportunities to derive additional and more refined data from each archaeological potsherd. In future research the team wants to investigate how different pottery types and cooking techniques (e.g. water boiling or roasting) could lead to different lipid distribution patterns within the ceramic matrix. This will also help to understand why some ceramic fabrics appear to yield consistently higher lipid contents than others and to derive these cooking-related data from archaeological samples.
“Mechanisms of lipid preservation in archaeological clay ceramics revealed by mass spectrometry imaging” by S. Hammann, D.J. Scurr, M.A. Alexander and L.J.E. Cramp. Proceedings of the National Academy of Sciences (2020)
More background information can also be found in a blog article about the paper.