PALAEOLIPIDOMICS: A NEW BIOMARKER APPROACH TO TRACE CEREAL AGRICULTURE IN PREHISTORY

The adoption of a cereal-based diet set in train some of the most fundamental shifts in the global history of modern humans, yet the process by which this was introduced into many parts of the world is not understood. More specifically, at locations where conditions were not favourable for cereal agriculture, a number of models have been put forward, proposing a staggered, drawn-out or even failed introduction of a cereal-based economy as alternatives to a swift and full-blown appearance of the entire farming 'package' of crops and livestock. This is important for determining i) the social mechanism by which farming spread across Europe and hence its societal impact and ii) the extent to which environmental and climatic constraints had to be overcome to establish agriculture in the long-term. However, testing this on a large scale is challenged by uncertainties in the archaeological record, which hampers our understanding of the adoption and adaptation of farming.
Here we propose tackling this through developing a methodology that enables us to trace the importance of cereal products in prehistory through biological markers (biomarkers) left in archaeological pottery used to process them. Reconstructing dietary change through patterns in fat (lipid) molecules extracted from the pores of unglazed pottery vessels is now a well-established approach that has developed over the course of over four decades. These preserved fingerprints in pots have enabled major patterns in human subsistence to be reconstructed, including earliest direct evidence for dairying in Europe and an abrupt and sustained shift away from marine economies in the British Isles lasting nearly 5000 years.
Much previous research has focused upon fats of animal origin; however, plant foods such as cereals, which ultimately became a key staple in many societies across the world at some point in time, are currently invisible using this approach. This is because cereals are low in fat content compared with animal fats, and because no identifying signature has yet been established that would attribute lipid residues of cereal origin unambiguously to this source.
We propose to address this through developing a novel 'paleolipidomics' approach: that involves looking at the whole profile of the components of modern grain lipids and in particular characterizing minor classes that together may act as identifiers for cereal-processing. Through degradation experiments, we will confirm the most robust suite of markers that will survive over archaeological timescales and then test their persistence through analysis of archaeological pottery sherds from Iron Age Britain and Neolithic Germany where there is strong archaeological evidence for a cereal-based economy. We will then employ a cutting-edge and highly sensitive analytical approach using accurate-mass gas chromatography-mass spectrometry to detect these signatures in archaeological pottery extracts from two key localities (Britain and the Eastern Baltic), testing the prevalence of cereal processing against models proposed for the introduction of farming to these regions ca. 6000 years ago.

We have identified the following users as benefiting from this research:

1. Wider public: general adult population and school age children. The wealth of archaeological and historical documentaries, historically-focused 'reality television programmes' and news headlines are testimony to a wider public fascination with our shared past. In particular, these reflect significant interest in the challenges faced by our ancestors (e.g. 'Twenty-four Hour in the Past') and our long-term relationship with key staples such as cereals and dairy products, which is becoming increasingly topical due to the surge in demand for gluten- and dairy-free products, which is currently being witnessed. This research will be of value to the interested general public through enriching their awareness of the long-term relationship of human societies and major modern food groups throughout Europe and the adaptability of past human populations.

2. Heritage sector: we envisage this research being used by museums to inform displays that communicate local and regional archaeology to their audiences. The research provide more detailed knowledge of the patterns of subsistence within regions in Europe and will furthermore provide direct insight into the actual usage of material culture in prehistory which can be compared over space and time.

3. Commercial sector: this research is of relevance to commercial scientists, breeders and agronomists with interests in the role, function and evolution of lipid metabolites in plants, with UK specialists connected via e.g. the MonoGram network (see Pathway to Impact). Specifically, there is increased interest in the role of lipid metabolites in the properties of cereal products as they play a significant part in changes in quality during storage, aspects of processing, and the end product (Day, 2004). Finally, there is also an increased interest in ancient types of wheat as healthy alternatives to bread wheat (Abdel-Aal et al., 1998), which is predicted to lead to wider growth for high value niche markets (Shewry 2009). Hence the lipidome of these ancient varieties, including constituents such as alkyl resorcinols, believed to have significant antioxidant properties (e.g. Gilwa et al. 2011), will be of significant interest.

4. Project staff: The postdoctoral research assistant will gain hands-on expertise in the most in cutting edge analytical techniques in mass spectrometry, of use for both an academic or industrial career. They will take forwards in their careers experience of networking with researchers and professional archaeologists and scientists and skills in oral and written dissemination in academic and lay contexts. The proposal will provide skills to the PI that transcend the academic sphere, through significantly enhancing technical expertise, statistical abilities and project management as well as through interaction with the public and school-age audiences.

Abdel-Aal E-SM et al. 1998. Cereal Foods World 43, 708-715; Day L. 2004. In Wrigley et al. (eds) Encylopaedia of Grain Science. Elsevier, Oxford, pp.157-165; Gilwa J. 2011. J Agric Food Chem 59(21), 11473-82; Shewry PR. 2009. Journal of Experimental Botany 60, 1537-1553