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SCHERD: a Study of Cuisine and animal Husbandry among Early farmers via Residue analysis and radiocarbon Dating

Final Report Summary - SCHERD (SCHERD: a Study of Cuisine and animal Husbandry among Early farmers via Residue analysis and radiocarbon Dating)

The overall aim of the SCHERD project is to improve our understanding of life in Ireland during the Neolithic, a key transformative period of Europe’s past. The project’s main objective is to identify the former contents of a range of Irish Neolithic pottery vessels, from different stages of the period and from different parts of the island, through systematic molecular and stable isotope analysis of both absorbed and surface residues from these vessels. The project’s second, complementary objective is to provide more secure date markers for the period by directly dating surface and absorbed residues from vessels in key assemblages.

In many parts of Europe the appearance of pottery is linked to the introduction of agriculture and in Ireland the presence of pottery is widely used as a dating proxy for the Neolithic and vice versa. However, we have little idea of some of the most basic information on how these vessels fitted into everyday life. What did they contain? What were different shapes and sizes of vessels used for? Did shifts in style represent real or significant turning points in the Neolithic? Molecular and compound-specific stable isotope analysis is answering many of these questions, and fundamentally altering our understanding of prehistoric farming – and prehistoric societies – across Europe. The presence of animal fats, distinguishable as dairy or adipose fats, and traceable in some cases to species, may be used as proxies for animal exploitation. Applying these analyses across geographic areas and through the Neolithic, aided by targeted radiocarbon dating, we can obtain ‘snapshots’ of how diet and economy, and even belief systems, changed over time and between different societies.

SCHERD has selected and sampled pottery assemblages from 15 archaeological sites. Theseare spread across the island of Ireland, date from all phases of the Neolithic (Early, Middle and Late; c. 4000 – 2500 cal BC) and include material from houses, enclosures, pit complexes and ceremonial sites. Lipids from nearly 500 pottery sherds have been extracted and these extracts screened via High Temperature Gas Chromatography (HTGC), revealing for the most part extremely well preserved mixtures characteristic of degraded animal fats. Average lipid yields across different site assemblages have ranged from 80μg to over 900 μg of lipid per gram of pottery, with individual pottery sherds yielding as much as 3600 μg/gram. These are some of the highest yields obtained for European prehistoric pottery so far and may be due to the acidic soils covering much of Ireland, which is thought to preserve the lipids particularly well.

Further analysis of lipid extracts via GC-Mass Spectrometry (GC-MS) and GC-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS) have demonstrated that many of these Irish Neolithic lipid mixtures are dominated by ruminant dairy fats, i.e. milk products from cattle or sheep. Significantly, the SCHERD project has demonstrated that ruminant milk fats are present in some of the earliest pottery assemblages so far dated – those from the Early Neolithic enclosures at Magheraboy, county Sligo and Donegore Hill, county Antrim (both early 4th millennium cal BC) – which is conclusive proof that dairying was part of the very earliest farming practices on the island. Previously considered a Bronze Age, or later, phenomenon, these results push back the history of dairying in this part of Europe by up to two thousand years. Moreover, milk appears to remain an important part of the diet through the Neolithic in Ireland, as dairy fats continue to be very prevalent in pottery assemblages from the Middle and Late Neolithic. Interestingly, the increasing importance of pigs in the Late Neolithic economy has been demonstrated in Britain (particularly southern Britain) and is readily detectable through pottery residues, but there is no conclusive evidence for such a switch in Ireland. Compound-specific stable isotope analysis of Irish lipid residues have confirmed that pig fats were almost entirely absent in Irish Late Neolithic vessels. Results from the SCHERD project are also indicating differences in lipid yields from different site types, e.g. house assemblages and enclosure assemblages, with pottery vessels from the former sites yielding much lower amounts of lipid. This may be to do with different patterns of processing, use and consumption across different site types.

The SCHERD project has also incorporated a programme of radiocarbon dating, targeting both encrusted surface residues and absorbed residues from pottery. Twenty samples have been submitted to the NERC Radiocarbon Facility at Oxford University and results are due in early October. Such direct-dating techniques are of clear importance for establishing a more accurate estimate of when vessels were in use. By providing new dates for key vessel types, the project will help create a higher resolution and more robust chronology for the Irish Neolithic, which will in turn inform wider European chronologies. Perhaps more importantly, SCHERD has shown that the carbon in lipids, absorbed into the matrix of clay vessels, frequently survives where other sources of carbon do not (e.g. charred plant macrofossils, bone collagen), usually as a result of acidic burial environments. If the radiocarbon dating programme is successful, i.e. if the radiocarbon age of the pottery lipids proves to be sufficiently accurate and of sufficient resolution, this method of dating could be of enormous use dating archaeological sites with otherwise poor preservation of organic remains. The positive impact on cultural heritage sites worldwide is potentially very significant.

In terms of overall impact, Ireland represents the end point of the ‘Neolithic revolution’ in Europe, geographically and chronologically, and is an important part of the wider picture. However, the Irish material has remained absent from the increasingly fine-grained and geographically wide-reaching studies on early farming societies, as large amounts of recently gathered data on the Irish Neolithic remain unpublished and inaccessible to researchers. The above results have placed a crucially important but underused Irish dataset in its European context, constituting an immensely significant step towards the more mainstream application of this important branch of archaeological science, which has become the best practice approach in Europe. Project results have also provided a range of new insights into Neolithic daily life, e.g. whether dairying was practised, and what foods were consumed, both within Ireland and in a broader European setting.