Building an Experimental Comparative Reference Collection for Lithic Micro-Residue Analysis Based on a Multi-Analytical Approach

Residue analysis applied to stone tools is a useful aid for better understanding their past function and, by extension, reconstructing early human behaviour. However, if the nature of residues found on the lithic tools is misinterpreted, so will be our understanding of their archaeological context. As a consequence, correctly identifying residues in the domain of lithic studies is of paramount importance. With this main goal in mind, we analysed different experimental materials likely to have been involved in daily tasks in the prehistoric context (e.g. bone, wood, meat). Microscopic analyses were then carried out using two (comparable) techniques: Optical Light Microscopy and Scanning Electron Microscopy. Also, energy dispersive X-rays spectroscopy (EDX or EDS) was applied to the experimental samples to determine their elemental composition. Advantages and disadvantages of both microscopic methods and their implications for correct residue identification are discussed. The distribution of residues on lithic surfaces is also considered. This study resulted in the construction of a data-set including both photographic material and EDX spectra for each residue analysed. The main result is that, compared to OLM scanning, SEM analyses highly improves the accuracy of residue identification.     

DNA from ancient stone tools and bones excavated at Bugas-Holding,Wyoming

DNA residues may preserve on ancient stone tools used to process animals. We studied 24 stone tools recovered from the Bugas-Holding site in northwestern Wyoming. Nine tools that yielded DNA included five bifaces, two side scrapers, one end scraper, and one utilized flake. The excavators did not handle three of these tools with bare hands, and they were sealed in separate plastic bags to minimize contact with modern DNA. Five sediment samples did not yield mammalian DNA. One tool contained DNA from three species, and these templates competed during polymerase chain reaction (PCR) amplification. DNA identifications suggested a butchery pattern indicative of a human population under resource stress or a broader range of industrial activities at Bugas-Holding. We describe several improvements in DNA residue analysis, including a more effective DNA recovery protocol, methods to measure sensitivity and inhibition of PCR in each sample, and strategies to surmount competition between templates during PCR.     

Swept under the rug: the problem of unacknowledged ambiguity in lithic residue identification

Microscopic analysis of organic residues on stone tools is used to interpret prehistoric stone tool functions. The morphology of some residues can be difficult to interpret, yet this ambiguity is rarely acknowledged in the literature. Our research seeks to understand the nature of this ambiguity by objectively identifying ambiguous residues in our reference collection. We trained four archaeologists in residue analysis using one part of our reference collection, then tested their ability to identify sixty-eight residues in another part of the same collection. Forty-eight of the residues in the test (70%) were correctly identified by three or all four subjects. We considered the remaining twenty residues, which were correctly identified by two or fewer of the subjects, to be ambiguous. These are most often in the hide-scraping, bone-scraping, and hardwood-scraping (macerated) categories, and tend to have an atypical morphology which falls in the range of variability of another residue category. Some of these residues also have optical properties which make them more difficult to image than others. We explore the potential for scanning electron microscopy (SEM) to improve residue identification in a second test. This test shows a modest improvement in identification success rates of ambiguous residues when SEM images are included. We conclude that while images from different types of microscopes can improve reliability of identification, some residues will always be ambiguous. Rather than being ignored, these ambiguities should be brought to light, closely examined, and published as such.     

Extracting residues from stone tools for optical analysis: towards an experiment-based protocol

The identification of residues is traditionally based on the distinctive morphologies of the residue fragments by means of light microscopy. Most residue fragments are amorphous, in the sense that they lack distinguishing shapes or easily visible structures under reflected light microscopy. Amorphous residues can only be identified by using transmitted light microscopy, which requires the extraction of residues from the tool’s surface. Residues are usually extracted with a pipette or an ultrasonic bath in combination with distilled water. However, a number of researchers avoid residue extraction because it is unclear whether current extraction techniques are representative for the use-related residue that adheres to a flaked stone tool. In this paper, we aim at resolving these methodological uncertainties by critically evaluating current extraction methodologies. Attention is focused on the variation in residue types, their causes of deposition and their adhesion and on the most successful technique for extracting a range of residue types from the stone tool surface. Based on an experimental reference sample in flint, we argue that a stepwise extraction protocol is most successful in providing representative residue extractions and in preventing damage, destruction or loss of residue.     

Small things in perspective: the contribution of our blind tests to micro-residue studies on archaeological stone tools

Our blind tests are distinctive for they were conducted on replicated stone tools used for a variety of tasks that included the processing of animal remains and plants. The analyst was required to differentiate an array of residues from microscopic morphological characteristics, using light microscopy. The original aim of our first tests was to assess the analyst's ability to identify a variety of plant and animal residues, but issues and problems that arose during the testing process made it clear that greater value might be gained from the lessons that we learnt about methodology and the direction for future micro-residue research. We show that problems identified during our first tests stimulated research. Amongst other things, we learnt to distinguish plant and animal remains more confidently than previously. Our residue analyses are firmly embedded in wider archaeological research and our tests help to explain why there are sometimes contradictions between the evidence from archaeologically recovered remains and residues on stone tools. A further outcome of the tests is that we have adopted a multi-stranded approach that provides a cautious, but secure strategy for identifying and interpreting use-residues. Our studies of contaminants through replications have also been invaluable for distinguishing incidental residues from use-related residues.     

Raman spectroscopy and scanning electron microscopy confirm ochre residues on 71 000‐year‐old bifacial tools from Sibudu,South Africa

Micro‐residue analysis of stone tools is generally performed with optical light microscopy and the visual observations are then compared with experimental, replicated pieces. This paper complements such archaeological research by providing physico‐chemical evidence. Raman spectroscopy and scanning electron microscopy have been used to confirm the presence of hematite on red‐stained medial and proximal parts of 71 000‐year‐old Still Bay bifacial tools from Sibudu Cave. Our results confirm the conclusion from optical light microscopy that the tools were hafted with an ochre‐loaded adhesive. However, we point to some instances when hematite residues are incidental or may be inclusions in the rock used to make the stone tools.     

DNA AND PROTEIN RECOVERY FROM WASHED EXPERIMENTAL STONE TOOLS*

Traces of protein and DNA are preserved on stone tools used to process animals. Previous research documents the identification of protein residues from tools sonicated in 5% ammonium hydroxide, but it remains untested whether the same treatment yields useable DNA. In this study we report both DNA and protein recovery using 5% ammonium hydroxide from residues on stone tools. We extracted 13‐year‐old residues from experimentally manufactured stone tools used to butcher a single animal. We also show that surface washing procedures typically used to curate stone tools remove only a small fraction of the DNA and protein deposited during animal butchery.     

Remains of the day-preservation of organic micro-residues on stone tools

Here I report on the decay processes of microscopic organic residues left on stone tool surfaces after their use. Residue analysis on ancient stone tools facilitates reconstruction of past activities. This study enables predictions about the circumstances under which ancient residues preserve. Experimental tool sets with modern residues were buried for a year in separate deposits at Sterkfontein, Sibudu (South Africa) and Zelhem (the Netherlands) whose pH and geomorphology varied, they were then analysed using light microscopy. Biological weathering mainly causes residue decay. In unstable environments rich in microbes and micro-organisms, residues decay quickly. From an archaeological perspective this means that sites that are stable, desiccated, waterlogged, extremely acidic or alkaline and extremely cold or hot sites. Different residue types have different preservation optima and this may lead to a preservation and perhaps interpretation bias. The preliminary predictive models presented in this paper could aid in the considered selection of sites and samples.     

Early and mid Holocene tool-use and processing of taro (Colocasia esculenta), yam (Dioscorea sp.) and other plants at Kuk Swamp in the highlands of Papua New Guinea

Recent multidisciplinary investigations document an independent emergence of agriculture at Kuk Swamp in the highlands of Papua New Guinea. In this paper we report preliminary usewear analysis and details of prehistoric use of stone tools for processing starchy food and other plants at Kuk Swamp. Morphological diagnostics for starch granules are reported for two potentially significant economic species, taro (Colocasia esculenta) and yam (Dioscorea sp.), following comparisons between prehistoric and botanical reference specimens. Usewear and residue analyses of starch granules indicate that both these species were processed on the wetland margin during the early and mid Holocene. We argue that processing of taro and yam commences by at least 10,200 calibrated years before present (cal BP), although the taro and yam starch granules do not permit us to distinguish between wild or cultivated forms. From at least 6950 to 6440 cal BP the processing of taro, yam and other plants indicates that they are likely to have been integrated into cultivation practices on the wetland edge.     

First results on thermally induced porosity in chlorite cooking vessels from Merv (Turkmenistan) and implications for the formation and preservation of archaeological lipid residues

Excavations at the ancient city of Merv in Turkmenistan have yielded a significant assemblage of ceramic and stone vessel fragments from contexts dating to the Sasanian and medieval periods (5th–13th centuries AD). Many of the vessel fragments are encrusted with apparent food residue deposits offering scope for organic residue analysis and the potential to compare the use of these two very different vessel types. To enable meaningful comparison we sought to establish whether the vessel stone (a talc-chlorite schist) can absorb and preserve organic residues indicative of past use. This paper reports the first investigation to address this question using standard methods for archaeological residue analysis coupled with study of the properties of the schist fabric and basic absorption experiments. The results demonstrate that heating during cooking, even at relatively low temperatures, modifies the stone microstructure by increasing its porosity. These pores enhance the absorption capacity of the schist fabric such that chlorite cooking pots can absorb and preserve sufficient organic residue to reflect the original processing of foodstuffs, as has been previously demonstrated for ceramic fabrics. Comparison of pore capacity, archaeological residue yield and experimental absorption indicates the significance of pore-size distribution for the relative retention and preservation of organic residues in these fabrics. The results of this study indicate that a wider range of archaeological material may be suitable for absorbed residue analysis than has previously been recognised. The findings also challenge previous assumptions concerning the relationship between the properties of chlorite vessels and their mode of use in Central Asia and Near East in antiquity.     

Assessing the reliability of pRIA for identifying ancient proteins from archaeological contexts

The use of immunological techniques for identifying the origin of proteins and inferring foodstuffs exploited by prehistoric occupations has been conducted for several decades. Cases of experimental laboratory and archaeological studies have shown the potential of these techniques for reliable results. However, very few of these case studies employ archaeological sites that have excellent preservation and high-resolution spatial contexts between identifiable faunal remains, features, and stone tools. We present an assessment of the identification reliability of one immunological technique, protein radioimmunoassay (pRIA), using faunal remains and stone tools from two sites from arctic and subarctic contexts. The results of this research indicate that, even in contexts with excellent preservation, the identifications produced by the pRIA technique are subject to misidentification and cross-reactions due to diagenetic alteration of proteins. We propose a higher minimum reaction value (percent binding of labeled antibody) that mitigates these effects, and renders the pRIA results more reliable for ancient, poorly preserved organic remains.     

Analysis of DNA from Ethnoarchaeological Stone Scrapers

Analysis of DNA residues on stone tools provides a direct method of determining what the tools were used on. However, little is known about the taphonomy of DNA on tools. The discovery of present-day, stone-tool using hide workers in Ethiopia therefore provides a unique opportunity to study the survival and authenticity of DNA residues on stone tools. We collected stone scrapers from contexts ranging from excavated to confirmed use, as well as unused scrapers to test for the presence of DNA residues. We amplified segments of the mitochondrial genome with PCR to determine which animal species a tool was used on. We were able to recover authentic DNA from scrapers of known use and from a subset of excavated scrapers. We did, however, also obtain DNA unrelated to the use of the tools. Thus, caution must be used when interpreting results of DNA analysis of stone tools.     

Experiments with Lithic Tools: Understanding Starch Residues from Crop Harvesting

Stone knives were used widely in Neolithic East Asia, presumably in the harvesting of grain crops, but their function has not been clearly understood due to the lack of study of residues from these tools. To address this issue, starch grain analysis was employed to study the residues on the surface of ancient stone knives and large amounts of starches were recovered. The sources of these starches, however, were not well understood, because harvesting of crops involves the cutting of stems rather than direct contact with starchy seeds. To determine whether harvesting could deposit these types of residues, we designed a simulation experiment using stone flakes to harvest ears of wheat, rice and foxtail millet, then analysed the residues on both the flakes and in the plant tissues. A large number of starch grains were found in the stems, including both typical morphotypes from seeds and newly described types that occur only in stems, which can be used as indicators of harvesting. Our study demonstrates that starch grains from residues on the surfaces of archaeological stone knives can indicate not only that the tools were used to harvest ears, but also the type of crops harvested.     

Evaluating protein residues on Gainey phase Paleoindian stone tools

Blood protein analysis provides a method for acquiring and interpreting archaeological data bearing on human–animal relationships. The present study makes use of cross-over immunoelectrophoresis (CIEP) and a large sample of stone tools (N = 130) from an early Paleoindian site pertaining to the Gainey phase (ca. 11,200 BP) of the Midwestern USA. Results are used to interpret toolkit organization and site structure, and indicate that hafted tools with longer use-life potentialities are more likely to be associated with preserved residues than are tools of a more ad hoc or situational character. Protein residues derived from cervids are the largest category of identified samples, a result consistent with an interpretation that these animals were important first-line resources of Gainey phase populations. The identification of caribou (Rangifer sp.) is notable. Interpretations of subsistence importance, however, must be tempered by an appreciation of the possible confounding effects of tool manufacture and maintenance in early Paleoindian contexts.     

The morphological identification of micro-residues on stone tools using light microscopy: progress and difficulties based on blind tests

Fifty-three stone flakes were knapped for a series of four blind tests on replicated flakes with residues derived from the processing of plant and animal products. Some flakes were hafted before use. Tests 1 and 2 were pioneering efforts published in 2004; lessons learned from these early studies shaped the new research reported here and lead to improved methodology and interpretive skills. A high level of accuracy was obtained for test 4. Test 3 showed that the rock type of a tool could influence the ability of the analyst to recognize and interpret residues. Test 4 in the series resulted in the most accurate interpretations because, prior to Test 4, identification difficulties experienced during the first three blind test sessions were addressed by examining many stone tools that had been used for various replicated tasks. The preparatory exercise was particularly useful for resolving issues that had previously caused problems for correctly identifying animal residues. The new work reported here highlights some of the difficulties that can be experienced in the morphological identification of microscopic organic residues, particularly the distinction between animal and plant residues. Some solutions for these problems are suggested.     

An experimental ethnoarchaeological approach to understanding the development of use wear associated with the processing of river cane for split-cane technology

Southeastern Indians have been using cane (Arundinaria spp.) for basketry and matting for thousands of years. Unfortunately, it is only under extraordinary preservation conditions that such items survive archaeologically. Inferring the production of split-cane technology requires an understanding of prehistoric manufacturing and processing techniques. It is hypothesized that stone tools were once used to process cane for use in split-cane technologies. In the Southeast, it is not uncommon to find stone tools with traces of plant use; however attributing wear to specific plants has been problematic. Pilot experiments, grounded on ethnoarchaeological observations, were conducted with river cane (Arundinaria gigantea) in collaboration with expert basket weavers in the Cherokee Nation. The experimental ethnoarchaeological program was designed to test the efficiency of stone tools in cane processing and document use wear through microscopic observations. The results found that non-retouched flakes were efficient for processing river cane and that the different stages of splint preparation resulted in the differential development of use-related wear. Additional experimentation with river cane is necessary to better define use wear and establish criteria for identification in archaeological contexts. Nonetheless, the collaborative and experimental approach undertaken demonstrated the utility of combining traditional archaeological methods with experimentation, ethnoarchaeology, and tribal knowledge.     

The Role of Fire in the Life of an Adhesive

The use of fire is essential for the preparation of hafting adhesives; both are suggested to be a proxy for distinguishing the technological expertise and complex cognition among Palaeolithic populations. While use of fire has been argued to exist from about 1.0 Ma onwards, evidence for adhesives in the Palaeolithic record is rare and fragmented. In spite of the close link between fire places and adhesives, no study has ever focussed on examining the impact of heat on adhesive deposition and preservation. This paper discusses the results of a combustion experiment that was undertaken to understand the impact of heat exposure on hafting adhesives. The results have significant implications for archaeological interpretations. Deposition in or near a fire proves to severely impact the types of residues that preserve on a stone tool. The vertically transferred heat is responsible for the loss of adhesives but also for the incidental production of adhesives and their deposition on stone tools. It can be hypothesised that the rare survival of adhesives on archaeological stone tools might not only be the result of direct contact with the fire but also the result of degradation due to heat from overlying fireplaces. If we are to improve our understanding of the preservation of adhesives, it is important to unstand the taphonomic processes that affect these adhesives, in particular heat alteration.     

Clues to Stone Tool Function Re-examined: Comparing Starch Grain Frequencies on Used and Unused Obsidian Artefacts

The identification of plant residues observed on prehistoric stone artefacts has often been used to inform on tool function without adequate consideration of potential contamination due to post-depositional processes. The paper redresses this balance by proposing a methodology which combines use-wear and residue analyses with systematic testing of depositional context to distinguish residues formed during tool use from accidental contamination. A case study involving obsidian artefacts from an open site in Papua New Guinea is used to illustrate the new approach. Starch grains, a class of residue which has had little attention outside Australia, were chosen as the focus of study because of their abundance at this site. The frequency of starch grains extracted from residues on stone artefacts was compared with those in sediments adhering to and adjacent to the artefact. A use-wear study conducted as a blind test provided an independent measure of whether the artefacts had been used. The frequency of starch grains was shown to be significantly correlated with used artefacts and not correlated with unused artefacts or the sediments. The case study demonstrates the importance of testing for contamination and also illustrates the benefit of studying starch grains as a class of plant residue.     

Assessment Techniques for Studying the Effects of Fire on Stone Materials: A Literature Review

ABSTRACT

Fire is one of the most severe threats to stone applied in civil engineering and architecture. In most cases, its effects are irreversible and have long-lasting repercussions. In addition to aesthetic alterations, fire can also induce important mineral-chemical, physical, and mechanical changes in stone. Research concerning the effects of fire on stone materials in recent decades has been providing valuable knowledge to inform present and future conservation and restoration actions. In this literature review, the properties and techniques used for studying the effects of fire on stone materials are appraised, summarized, and compiled. A comprehensive and practical overview of those effects is also given. Open porosity and P-wave ultrasonic velocity are the physical and mechanical properties that have been studied most. Other frequently researched areas include chemical-mineralogical changes, color, density, water absorption, uniaxial compressive strength, and modulus of elasticity are also very frequently investigated.