Stephanie N. Dudd

Direct chemical evidence for widespread dairying in prehistoric Britain

Domesticated animals formed an important element of farming practices in prehistoric Britain, a fact revealed through the quantity and variety of animal bone typically found at archaeological sites. However, it is not known whether the ruminant animals were raised purely for their tissues (e.g., meat) or alternatively were exploited principally for their milk. Absorbed organic residues from pottery from 14 British prehistoric sites were investigated for evidence of the processing of dairy products. Our ability to detect dairy fats rests on the observation that the δ13C values of the C18:0 fatty acids in ruminant dairy fats are ≈2.3‰ lower than in ruminant adipose fats. This difference can be ascribed to (i) the inability of the mammary gland to biosynthesize C18:0; (ii) the biohydrogenation of dietary unsaturated fatty acids in the rumen; and (iii) differences (i.e., 8.1‰) in the δ13C values of the plant dietary fatty acids and carbohydrates. The lipids from a total of 958 archaeological pottery vessels were extracted, and the compound-specific δ13C values of preserved fatty acids (C16:0 and C18:0) were determined via gas chromatography-combustion-isotope ratio mass spectrometry. The results provide direct evidence for the exploitation of domesticated ruminant animals for dairy products at all Neolithic, Bronze Age, and Iron Age settlements in Britain. Most significantly, studies of pottery from a range of key early Neolithic sites confirmed that dairying was a widespread activity in this period and therefore probably well developed when farming was introduced into Britain in the fifth millennium B.C.

Free and bound fatty acid oxidation products in archaeological ceramic vessels

While oxidation products of unsaturated fatty acids, for example dicarboxylic acids (hereafter diacids), must form during the use of unglazed ceramic vessels for the processing of animal and plant products, such components have never been observed during studies of absorbed lipids. Their absence from the extractable lipid fraction is presumed to be the result of their loss from potsherds through groundwater leaching. Lipid oxidation products including short–chain dicarboxylic acids, ω–hydroxy acids and longer–chain hydroxy and dihydroxy acids have now been observed as components probably covalently bound into solvent insoluble residues of potsherds recovered from waterlogged deposits. These components were only revealed following alkaline treatment of the insoluble residues. A similar mixture of diacids was observed in high abundance in the free lipid fraction of vessels recovered from an exceptionally arid deposit where groundwater leaching would never have occurred. These results confirm the formation of oxidation and probable polymerization products of unsaturated fatty acids during vessel use and burial.

Fuel for thought? Beeswax in lamps and conical cups from Late Minoan Crete

What was burned in lamps in the prehistoric Mediterranean ? Olive oil, as one would first suppose ? Analysis of absorbed lipids preserved in the fabric of lamps and conical cups from the Minoan site of Mochlos in eastern Crete shows for the first time that beeswax was used as an illuminant.

New Criteria for the Identification of Animal Fats Preserved in Archaeological Pottery

R.P. Evershed, H.R. Mottram, S.N. Dudd, S. Charters, A.W. Stott,G.J. LawrenceOrganic Geochemistry Unit, School of Chemistry, Cantock’s Close,University of Bristol, Bristol, BS8 1TS, UKA.M. GibsonClwyd-Powys Archaeological Trust, 7a Church Street, Welshpool Powys,SY21 7DL, UKA. ConnerCambridgeshire County Council Archaeology Unit, Fulbourne CommunityCentre, Haggis Gap, Fulbourne, Cambridge, CB1 5HD, UKP.W. BlinkhornOxford Archaeological Unit, Janus House, Osney Mead, Oxford, OX2 0ES, UKV. ReevesCentral Archaeological Services, English Heritage, Fort Cumberland,Fort Cumberland Road, Eastney, Portsmouth, PO4 9LD, UK

Formation of long-chain ketones in ancient pottery vessels by pyrolysis of acyl lipids

Abstract Structural and Isotopic (δ 13 C) evidence indicates the formation of series of long-chain ketones in archaeological pottery can occur by condensation of long-chain carboxylic acids. The formation of the ketones is confirmed by pyrolysis of free fatty acids or triacylglyecrols in the presence of fired clay matrix.

Formation of long-chain ketones in archaeological pottery vessels by pyrolysis of acyl lipids

Abstract Studies of organic residues preserved in unglazed archaeological pottery have revealed the presence of homologous series of long-chain ketones containing 29–35 carbon atoms. The C31, C33 and C35 ketones are particularly abundant and exhibit a distinct monomidal distribution. The presence of long-chain ketones in potsherds is usually ascribed to the absorption of epicuticular waxes into the pottery fabric during the cooking of leafy vegetables. However, compound specific stable carbon isotope (δ13C) analyses of the individual lipids present in the potsherd extracts, in combination with detailed structural information, indicates that these ketones do not derive from plant waxes. Isotopic and structural analysis of the fatty acids, which always co-occur with the ketones, suggest that a precursor-product relationship exists. Micro-scale pyrolysis of a range of free fatty acids and triacylglycerols in the presence of various inorganic matrices was undertaken in exploring the possibility of an abiological route to the formation of the ketones. Depending on the pyrolysis conditions employed, substantial yields of long mid-chain ketones were formed which were structurally and isotopically congruent to those observed in the ancient potsherds. The ketones are formed by ketonic decarboxylation (a type of head to head condensation reaction), probably involving fatty acid metal salts as intermediates, the metal being provided by the inorganic matrix. Apart from the abundant long mid-chain ketones various other products such as methylketones, methyl esters, alkanes, alk-1-enes and homologous series of minor ketones are formed as secondary pyrolysis products. These latter products are not found in the pottery probably due to less vigorous thermal conditions achieved during the original use of the vessel compared with those attained in the laboratory pyrolysis experiments. Evidence for this comes from the formation of the fatty acid methyl esters which are only produced under the most forcing of pyrolysis conditions.

UNUSUAL TRITERPENOID FATTY ACYL ESTER COMPONENTS OF ARCHAEOLOGICAL BIRCH BARK TARS

Abstract At least three series of previously unreported components of ancient birch bark tars have been identified by electron and chemical ionisation mass spectrometry as comprising betulin (lup-20(29)-en-3β,28-diol), lupa-2,20(29)-dien-28-ol and lupeol esterified to fatty acids. Since such components are not present in fresh bark or pyrolysates thereof it appears that they result from the intentional mixing of birch bark tar and animal fat in antiquity.

Direct detection of maize in pottery residues via compound specific stable carbon isotope analysis

Discovering what was cooked in a pot by identifying lipids trapped in the potsherds has been a highly successful method developed in recent years. Here the authors identify a compound which shows the pots had been used to process maize – probably the most important foodstuff in later prehistoric North America. The uptake of maize is confirmed as coincident with the Mississippian fluorescence.