Changing Patterns of Marine Product Exploitation in Human Prehistory via Biomarker Proxies in Archaeological Pottery

Lead Research Organisation: University of Bristol
Department Name: Chemistry

Abstract

The availability and high nutritional value of marine resources means that they should have been a conspicuous component of prehistoric coastal food economies. However, finding evidence for the intensity of marine exploitation in the archaeological record is problematic, due in part to the poor survival and recovery of fish remains, the processing of marine foods and the rarity of fishing paraphernalia or other related artefacts. Stable carbon and nitrogen isotope signals for marine foods imprinted in human bone collagen were initially believed to circumvent these problems, based upon the principle that 'you are what you eat'. Evidence from isotopic analyses of human remains suggests that coastal and island Mesolithic people did utilise marine foods but that the Neolithic, after the adoption of farming, foods from the sea were abandoned. These data suggest that farmers throughout prehistory, and into historical times, negotiated new ways of living and turned their backs on the sea. However, recent critiques of these interpretations have noted that they are at odds with the archaeological evidence for the continued exploitation of marine resources throughout prehistory at sites along the Atlantic seaboard of Europe. This may signify that collagen isotope analysis is not sensitive enough to detect low or sporadic consumption of marine protein, nor will it detect the exploitation of marine fats and oils. Therefore, tracing changing patterns of marine exploitation throughout prehistory still pose an archaeological and scientific problem. Very significant recent findings in our laboratory have revealed a new way to detect the processing of marine products at a highly sensitive level. Organic residues from commodities prepared in unglazed pottery can become absorbed into the ceramic fabric; these ancient residues can then be extracted and characterised thousands of years later. Until now, marine fats have been difficult to identify since the diagnostic compounds in fresh fats degrade very rapidly upon burial. However, we have recently identified several new classes of highly diagnostic compounds derived from marine lipids, which persist over archaeological timescales. We have also shown that amino acids surviving in pottery can offer further insights into the commodities processed in the pottery vessels. This project will further investigate the origins of these novel compounds and develop a highly sensitive method for detecting them at very low concentrations in archaeological pottery. We will then use these biomarker compounds to track prehistoric patterns of marine food consumption, beginning with the early Neolithic. Pottery would be obtained from a range of Scottish and Irish sites where marine resource exploitation would have continued alongside the introduction of farming, albeit possibly at a lower level. We will also investigate pottery from Neolithic mainland coastal and inland sites, including Ireland, Scotland and northern Iberia, in order to compare how contemporary peoples were exploiting their environment. Where longer sequences of occupation exist, we will explore changing patterns in marine resource exploitation through time. Island sites, such as Northton on Lewis and Eilean Domhnuill in Loch Olabhat, which have evidence for settlement from the early Neolithic through to the medieval periods, offer opportunities for this part of the investigation. Likewise, long-lived mainland sites exist in Ireland and the Iberian northern peninsula; in the latter recent investigations have suggested both the adoption of Neolithic traditions by indigenous Mesolithic hunter-gatherers and the colonisation of incoming farmers. The refinement and implementation of these new marine biomarker proxies therefore offer the potential for new insights into changing patterns of marine resource exploitation by humans in antiquity at a resolution unachievable using more traditional approaches.

Publications

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Roffet-Salque M (2017) From the inside out: Upscaling organic residue analyses of archaeological ceramics in Journal of Archaeological Science: Reports

 
Description This project has successfully verified, refined and implemented new protocols for the highly sensitive detection of aquatic product exploitation and processing in prehistory and applied this to a large number of archaeological sites on the Atlantic seaboard, providing new insights into changing subsistence strategies at prehistoric coastal and island locations. Specifically, we have achieved the following outputs:

1. Through dosing pottery with a range of pure fatty acid standards and fats/oils from ca. 40 marine shellfish, fish and mammals and heating in vacuo, we have investigated the formation of aquatic biomarkers from heating lipids and extensively tested and verified the product-precursor relationship between polyunsaturated fatty acids (PUFAs) and _-(o-alkylphenyl)alkanoic acids (APAAs) of the same carbon chain length.

2. Using modern reference lipids and best-preserved archaeological lipid residues, we have refined and implemented protocols for detecting aquatic biomarkers, including APAAs and vicinal diols (DHYAs) using GC/MS in selected ion monitoring mode.

3. We have investigated _13C values from saturated fatty acids from nearly 100 individual fish, shellfish and marine mammals, obtained from non-farmed locations from UK or Scandinavian waters. A large reference dataset of replicated values from a range of different species consequently now exists, demonstrating the characteristically depleted/enriched values from freshwater and marine specimens respectively and highlighting intra- and inter-species variability.

4. These lipid biomarker and stable isotope proxies have been applied to archaeological lipid extracts from 550 sufficiently well-preserved lipid residues extracted from a total of 917 sherds. These sherds represent 41 Neolithic coastal sites and a further six Bronze Age, six Iron Age and three Viking/Norse assemblages from the Outer Hebrides, Shetland and the Orkney Isles. We have demonstrated the utility of a highly sensitive biomarker approach and have been able to trace an increasing emphasis on aquatic resources over five millennia.

5. The PhD studentship has resulted in an extensive dataset of 622 faunal baseline collagen _13C and _15N values from insular locations. Newly-generated and existing stable isotope data and faunal assemblage data have been collated and interpreted from 78 sites on the Outer Hebrides and Northern Isles and the integration of these findings with the main project have confirmed and enhanced our conclusions from the pottery residues



As direct results of this programme of research, we have demonstrated unequivocally through the integration of lipid biomarker, archaeozoological and stable isotope data that marine products were an insignificant resource during the Neolithic on the British Isles, even at coastal and island locations, only to re-emerge relatively late in prehistory. Conversely, dairying was an extremely important commodity especially during the earliest Neolithic, with dairy fats present in an exceptionally high number of vessels. Our findings have major implications for palaeodietary research and have already been disseminated at a range of national and international conferences, with themes covering archaeological science, dietary evolution, regional archaeology and the Mesolithic/Neolithic transition.
Exploitation Route The public have a seemingly insatiable interest in archaeology and we regularly promote interest in science via public and schools lectures in this context. For example, at the start of 2009 we began the development of the 'The Palaeodetectives' display as an outreach tool to promote the science we undertake. Our focus is on using cutting edge analytical chemistry for the study of modern and ancient environments, on archaeological to geological timescales. Central to the display is a computer game played on touch-screens, which enables the user to learn about the natural world in the past and how analytical chemistry is used to investigate it. The public are invited to 'solve' case studies (drawn from our published work in high profile journals) from around the globe on the basis of historical, geographical and chemical information presented to them. The "Cases" range from ancient agriculture to crude oil formation. The game is designed for any age and appeals to a wide range of interests. In addition to the 'The Palaeodetective' game, the exhibit includes a large pictorial display and molecular models on two large archaeological and geological sedimentary columns (see image below). The exhibit was originally created for the Royal Society Summer Science Exhibition 2009. More recently we have taken part in Discover 2010, organised by the University's Centre for Public Engagement (CPE), and were invited to the Festival of Nature in 2011, an annual event organised by the Bristol Natural History Consortium, which typically attracts 25,000 visitors and over 200 organisations ranging from environmental and conservation organisations to food and Fair Trade products. We are continuing to develop this resource and have recently made available an on-line version for access by the general public and schools. A large part of our reference datasets and analytical protocols is now published in RCMS and in press as a chapter in Treatise on Geochemistry: Archaeology and Anthropology and our archaeological data are already in press or published in three articles. Five further papers are in preparation, with two in advanced stages of preparation. In addition, a highly-skilled PhD student, experienced in archaeozoology and stable isotope analysis, will graduate shortly. Significantly, the PDRA working on the project has been appointed to a permanent Lectureship in Archaeology and Anthropology. The technician who worked on the project is now undertaking a PhD part funded by the NERC.
Sectors Agriculture, Food and Drink,Culture, Heritage, Museums and Collections,Other

URL http://www.chemlabs.bris.ac.uk/outreach/resources/Palaeodetective.html
 
Description U.K. Archaeological Sciences (Reading, September 2011) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked questions and discussion.

To be confirmed.
Year(s) Of Engagement Activity 2011
 
Description . (Freie Universit├Ąt, Berlin, Research seminar, Institute of Prehistoric Archaeology (Berlin, July 2013) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked questions and discussions.

To be confirmed.
Year(s) Of Engagement Activity 2013
 
Description Bristol Bright Night Research Tapas: 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Sparked questions and discussion.

To be confirmed.
Year(s) Of Engagement Activity 2014
 
Description European Association of Archaeologists (Pilsen, Czech Republic. September 2013); 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked discussion afterwards.

To be confirmed.
Year(s) Of Engagement Activity 2013
 
Description Hebridean Archaeological Forum (South Uist, September 2010). 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked questions and discussion.

To be confirmed.
Year(s) Of Engagement Activity 2010
 
Description Theoretical Archaeology Group (Liverpool, 2012). 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked questions and discussion afterwards.

To be confirmed.
Year(s) Of Engagement Activity 2012
 
Description U.K. Archaeological Sciences (Reading, September 2011) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked questions and discussion afterwards.

To be confirmed.
Year(s) Of Engagement Activity 2011