ON ISOTOPES AND OLD BONES*

This review charts the developments and progress made in the application of stable light isotope tools to palaeodietary adaptations from the 1970s onwards. It begins with an outline of the main principles governing the distribution of stable light isotopes in foodwebs and the quality control issues specific to the calcified tissues used in these analyses, and then proceeds to describe the historical landmark studies that have marked major progress, either in their archaeological applications or in enhancing our understanding of the tools. They include the adoption of maize agriculture, marine‐focused diets amongst coastal hunter–gatherers, trophic level amongst Glacial‐period modern humans and Neanderthals, and the use of savannah resources by early hominins in Africa. Particular attention is given to the progress made in addressing the challenges that have arisen out of these studies, including issues related to the routing of dietary nutrients. I conclude with some firm, and some more speculative, pointers about where the field may be heading in the next decade or so.     

ORGANIC RESIDUE ANALYSIS IN ARCHAEOLOGY: THE ARCHAEOLOGICAL BIOMARKER REVOLUTION*

Organic residue analysis utilizes analytical organic chemical techniques to identify the nature and origins of organic remains that cannot be characterized using traditional techniques of archaeological investigation (because they are either amorphous or invisible). The field is founded upon the principle that the biomolecular, or biochemical, components of organic materials associated with human activity survive in a wide variety of locations and deposits at archaeological sites. The archaeological information contained in organic residues is represented by the biomolecular components of the natural products that contribute to the formation of a given residue. By applying appropriate separation (chromatographic) and identification (mass spectrometric) techniques, the preserved, and altered, biomolecular components of such residues can be revealed. Once identified, the Archaeological Biomarker Concept can be applied, wherein the structure and even isotopic composition(s) of a given biomolecule or suite of biomolecules (the ‘chemical fingerprint’) can be related to the compositions of organisms exploited by humans in the past. As the organic residue field emerges from its pre‐paradigmatic phase, and the organic residue revolution gathers pace, the way is open for challenging many long‐held archaeological hypotheses and offering new perspectives on the study of human activity in the past.     

Impact of Pollution at a Stone Age Rock Art Site in Oslo, Norway, Studied using Lead and Strontium Isotopes

Naturally occurring strontium and lead isotopes were used to study the impact of anthropogenic pollution on a c. 4500-year-old rock carving in Oslo, Norway. Strontium analyses have shown that road-salt from de-icing of a nearby road has accumulated in the soil surrounding the carving. Upon rainfall this salt is redissolved and drains over the rock carving. Analyses of the lead isotopic system have confirmed the impact of traffic from the nearby road on the rock carving site, but also indicate other sources of lead in the Oslo area and pollution in general. The rock carvings at Ekeberg are at high risk as, apart from natural weathering, they are exposed to the deposition of road salt, emissions from nearby traffic, local and long distance atmospheric pollution and meteorological inversion effects during the winter.     

IN VITRO DECOMPOSITION OF BONE COLLAGEN BY SOIL BACTERIA: THE IMPLICATIONS FOR STABLE ISOTOPE ANALYSIS IN ARCHAEOMETRY*

To understand biogenic collagen type I decomposition and to establish how diagenesis may bias archaeometric data, modern mammalian bone was inoculated with a selection of ubiquitous soil bacteria. The presence of exogenous microbial biomass in the inoculated specimens was then checked microscopically prior to collagen extraction. The experimentally degraded bone collagen showed altered amino acid compositions, attributable to the selective breakdown of certain amino acids by the bacteria. While both the bulk collagen extract and the single amino acids exhibited shifts to more negative δ¹³ C-values, enrichment was recorded for general δ¹³ N, and a depletion trend relative to unaltered collagen was observed for individual amino acid δ¹³ N. One explanation for the enrichment of the global δ¹⁵N-values is cleavage of peptide bonds, which leaves ¹⁵ N within the substrate, while the change of ¹³C is mostly due to the altered amino acid composition. On the other hand, possible repolymerization of cleavage products under experimental conditions may also be responsible for the depletion trend of individual amino acid δ¹³C- and δ¹⁵ N-values. This paper discusses the results as a basis for the development of a method for the reconstruction of the isotopic abundance of the original collagen, using the amino acid composition of the degraded product, the contribution of individual amino acids to its global δ-values and of isotope discriminations implied in the microbial decomposition.     

ONLY TIME WILL TELL: A REVIEW OF THE METHODOLOGY OF DIRECT ROCK ART DATING

Epistemology has not kept pace with the progress experienced in the direct dating of rock art. This paper reviews the experimental methods that have been developed in recent years. While many do provide important information about the possible age of rock art, it is of concern that the precipitate archaeological interpretations these data are used for are often not warranted. Some are attributable to not understanding the severe qualifications that apply to most dating results, others perhaps to over-enthusiasm on the part of some researchers. The introduction of archaeological dynamics into direct dating of rock art threatens the reliability of this young methodology. Some of the pitfalls are considered in this paper, and a general rationale for the direct dating of rock art is developed.     

PALAEOCLIMATIC IDENTIFICATION BASED ON AN ISOTOPE STUDY OF TRAVERTINE FROM THE COPPER AGE SITE AT LOS MILLARES,SOUTH-EASTERN SPAIN*

Remains of an aqueduct from the Copper Age settlement of Los Millares have been studied. The isotope results (—7‰ < δ¹⁸O — 5.3‰) show that the aqueduct was used to transport fresh water at room temperature. The results are inconsistent with the aqueduct being used for hot water transport or as a container for water exposed to evaporation processes. Both isotopic and mineralogical results were useful in identifying the origin and use of building materials and also in determining climatic conditions during the time of the settlement occupation.     

OBSIDIAN IN THE MEDITERRANEAN AND THE NEAR EAST: A PROVENANCING SUCCESS STORY

Obsidian provenancing studies comprise one of the most productive and successful research programmes of archaeological science. Obsidian characterization has been successful because workable obsidian is homogeneous on a small scale, analysable by a large number of methods, and is restricted to a small number of mainly readily distinguishable geological sources. Analytical, dating, source, and trade studies within the western Mediterranean, central and eastern Europe, the Aegean, and Anatolia and the Near East during the last 30 years or so are reviewed. Research has shown that distributions are mainly separate in the four regions examined, and that obsidian was traded up to 900km in the prehistoric period. Publications on obsidian in the areas under review reached a peak of frequency in the later 1970s and 1980s, but have now decreased in number. This may reflect changing fashions in archaeometric studies, and a current lack of routine application of the provenancing methods developed.     

CATHODOLUMINESCENCE OF WHITE MARBLES: AN OVERVIEW*

Identifying the source area of white marbles has long been a problem in archaeology. To address this problem, about 1000 samples from known Classical quarrying areas in Greece, Italy and Turkey were analysed using cathodoluminescence. Twenty-one cathodomicrofacies were recognized, each of which generally characterizes a given area. In cases where the cathodomicrofacies is common to more than one area, δ¹³C and δ¹⁸O signatures provide an effective complementary dataset which allows additional distinctions. Determination keys for the 21 cathodomicrofacies observed are proposed based upon their principal cathodoluminescence colour, and their stable isotopic signature.     

PROVENANCE DETERMINATION OF NEOLITHIC TO CLASSICAL MEDITERRANEAN MARBLES BY STABLE ISOTOPES*

Two stable isotopic data bases for ?¹³C and ?¹⁸O values of marble have been accumulated: (1) 590 analyses from 42 Classical quarries of Greece, western Turkey, Tunisia, and Carrara, Italy, and (2) potential Early Bronze Age (EBA) marble sources in the central Cyclades, comprising 192 analyses from 16 sites on the islands of Paros, Naxos, Ios, and Keros. The data bases include the most important marble occurrences in the eastern Mediterranean and so can be used to source artefacts of any age. Neolithic artefacts found at Franchthi Cave, where no marble occurs locally, have been attributed to the Peloponnese and the Cyclades, direct evidence for early trade. In the Cycladic EBA, Naxos and Keros were the principal marble sources for the abundant artefacts found at Keros. The commercial marble trade in Archaic Greece began in the central Cyclades where the tradition apparently went back some 5000 years, to the Neolithic. Classical Greece and especially Rome expanded the number and locations of commercial marble sources throughout the Mediterranean.     

IDENTIFICATION OF FORGERIES BY MEASURING TIN ISOTOPES IN CORRODED BRONZE OBJECTS*

The reliable identification of fakes consisting of bronze often presents problems, because traditional methods such as stylistic studies, optical microscopy, chemical analysis or X‐ray diffraction of the corrosion may not be conclusive. We present a method that is based on the comparison of the tin isotope ratios ¹²²Sn/¹¹⁶Sn and ¹¹⁷Sn/¹¹⁹Sn in the metal and in the adherent corrosion layer. An artificial patina is usually generated within a short time period. It has been observed that such a procedure leads to a depletion of the light tin isotopes in the corrosion layer, while in naturally corroded authentic archaeological objects no isotopic fractionation has been detected. The method has also been applied to archaeological objects and it could be confirmed, among other examples, that the famous ‘Sky Disc of Nebra’ is authentic.