Development and application of a comprehensive analytical workflow for the quantification of non-volatile low molecular weight lipids on archaeological stone tools

Source determination of use-related residues on prehistoric stone tools is especially challenging, due to issues related to preservation, contamination and the contribution of residues from multiple sources. To increase confidence in this process, an analytical workflow was developed to include: (1) a sampling strategy that retains spatial information of the recovered residues and enables monitoring of environmental contamination; and (2) a sensitive and selective gas chromatography-tandem mass spectrometry (GC-MS/MS) procedure to quantify non-volatile low molecular weight lipids on stone artefacts. This workflow was applied to 14 stone artefacts excavated from deposits at Liang Bua, a limestone cave on the Indonesian island of Flores. These artefacts range in age between ∼14 000 and 1000 years old, and were preliminarily classified as either potentially showing traces of use (n = 7) or not (n = 7) using low magnification microscopy. Residues were sampled by direct solvent extraction off the surface of the artefacts. The aliquots were spiked with internal standards and derivatised. The trimethylsilyl derivatives of 40 saturated fatty acids, sterols, di- and tri-terpenoids and their analogues were quantified using optimised multiple reaction monitoring (MRM) transitions. Six of the potentially used artefacts contained sterols, phytosterols and terpenoids, either individually or in combination, whereas none of these compounds was commonly found on the seven artefacts preliminarily classified as unused. This suggests that these six artefacts may have been used as implements to process resources, and provides scope for further investigation. This workflow can also be adapted for the analysis of other archaeological objects

Combined organic biomarker and use-wear analyses of stone artefacts from Liang Bua, Flores, Indonesia

Organic biomarker and lithic use-wear analyses of archaeological implements manufactured and/or used by hominins in the past offers a means of assessing how prehistoric peoples utilised natural resources. Currently, most studies focus on one of these techniques, rather than using both in sequence. This study aims to assess the potential of combining both methods to analyse stone artefacts, using a set of 69 stones excavated from the cave site of Liang Bua (Flores, Indonesia). Prior to chemical analysis, an initial inspection of the artefacts revealed potential use-wear traces but no visible residues. Gas chromatography mass spectrometry (GC-MS) analysis, including the targeting of 86 lipids, terpenes, terpenoids, alkanes and their analogues, found compounds with plant or animal origin on 27 of the 69 stones. The artefacts were subsequently cleaned, and use-wear analysis identified traces of use on 43 artefacts. Use-wear analysis confirmed traces of use on 23 of the 27 artefacts with potential use-residues that were determined by GC-MS. The GC-MS results were broadly consistent with the functional classes identified in the later use-wear analysis. This inclusive approach for stone artefact analysis strengthens the identifications made through multiple lines of enquiry. There remain conflicts and uncertainties in specific cases, suggesting the need for further refinement and analyses of the relationships between use-wear and residues

Extending the chronology for Blombos Cave, South Africa: Further evidence for the origins of modern human behaviour

Behavioural modernity, however defined, is considered to be the key distinctive feature separating Homo sapiens from earlier hominid lineages. While the fossil and genetic records imply that modern human morphology evolved in Africa between 250 and 150 thousand years (ka) ago, there is currently no unification regarding the timing or geographical origins of modern human behaviour (MHB). An increasing body of evidence suggests modern behaviour was present during the African Middle Stone Age (MSA). Defining the origins of MHB requires accurate and precise chronologies of when they first emerged. Blombos Cave in South Africa has yielded a collection of well-preserved cultural material from within the MSA layers. These include bone tools, shell beads, engraved ochre slabs and an assemblage of stone artefacts which are believed to represent a dynamic tool industry, the Still Bay (SB). More recently, ochre containers which may contain evidence for the ingredients used to produce paint, have been found in the lower layers of the cave, along with a tool kit, such as bone spatulas, that suggest an even earlier origin of MHB. The likely symbolic significance of these artefacts implies cognitive sophistication of MSA hominids and modern human behaviour previously only asserted in LSA people. Examination of both sediments and anthropogenic deposits within the MSA levels have allowed the MSA layers of Blombos Cave to be subdivided into separate phases and layers. Each of these has been systematically dated in this study using optically stimulated luminescence (OSL) dating techniques. The improved temporal resolution of this site contributes to the debates regarding the key mechanisms behind the emergence of MHB. Two leading theories regarding the emergence of MHB include: 1) environmental change, and 2) demographic change. OSL ages of sediments associated with these MSA levels suggest the SB industry occurred between 70 and 80 ka ago, with the other symbolic behaviours being recognised at ~110 ka. Such ages imply that MHB was present in southern Africa during the MSA and that it occurred sporadically, possibly as an outcome of increased human population and environmental conditions that were happening concurrently

Quandong stones: A specialised Australian nut-cracking tool

The quandong or native peach (Santalum acuminatum R.Br.) has been recognised as an important and tasty food resource among Aboriginal Australians in arid and semi-arid areas of southern Australia. It is valued for its fruit that is consumed raw or dried, and for its kernel, which is eaten raw or ground into paste for medicinal and skin care purposes. This paper reports on a study of ground stone implements within the Murray Darling Basin that has identified quandong stones as a distinct type of implement made specifically for the efficient cracking of quandong nuts. Data are presented on 1,327 ground stone implements from collections in 12 different locations in the Murray-Darling Basin (MDB), an area almost completely devoid of stone sources. Given the paucity of stone, multi-purpose use of implements is widely documented. Although it was common to find pits present in mortars and other ground stone tools demonstrating multiple functions, including use as anvils, a class of single purpose stones with multiple pits and distinctive form was identified. Most of these were found in areas known for groves of quandong and four were analysed for use-wear and residues along with two other ground stone items from the MDB. The results support their identification as specialised anvil stones for cracking quandong nuts

Documenting scarce and fragmented residues on stone tools: an experimental approach using optical microscopy and SEM-EDS

Residue analyses are widely applied to studies of stone tool function and can be a powerful method for determining the past tool use(s), especially when combined with other functional investigations such as usewear and technological analysis. Experimental work has shown that optical microscopes and the scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS) are reliable instruments for identifying intact tool residues. However, little experimental work has aimed to document residues that show various stages of degradation or when abundance is low. We combined traditional optical microscopy and the SEM-EDS to identify the advantages and challenges of each technique when looking at progressively smaller and more fragmented residues following more aggressive stages of cleaning, burial and soaking in a weak acid/base solution. We found that large quantities of intact residues on unwashed stone tools show distinctive morphological features under optical microscopes and the SEM-EDS can be used to document residues under extremely high magnifications and to determine their elemental compositions. After the various stages of washing, we found that residues became highly fragmented and were restricted to common stone features like the micro-cracks/scars along the working edge. These residues were often difficult to characterise using optical microscopes but the SEM-EDS proved highly useful. The weak acid/base solutions caused some residues to become physically altered or modified their elemental composition. Buried tools reduced the abundance of use-residues and introduced additional non-use-related contaminant particles that affected EDS measurements and lead to less reliable residue interpretations

Integrating SEM-EDS in a sequential residue analysis protocol: Benefits and challenges

Residue analysis can be a useful way to determine the past functions of archaeological tools, particularly when teamed with other functional investigations such as usewear and technological analyses. The most common approach for residue analysis is through the use of optical microscopes, which can be used to visually identify in situ residues directly from the tool surface (with reflected light microscopes, RLM), as well as in water extractions sampled from the utilised tool edges (with transmitted light microscopes, TLM). Recently, the scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS) has shown great potential for archaeological residue analysis as it can provide high-resolution images at very high magnifications as well as elemental analysis of adhering material. An advantage of this instrument is that it is capable of operating in low vacuum or environmental mode, allowing specimens to be examined uncoated and without additional preparation, so that residues can be documented/analysed in situ on the stone. In this paper, we propose a sequential protocol for the identification of tool residues using various optical light microscopes in combination with the SEM-EDS, on residues documented both in situ on stone tools and those removed from the stone substrate in solvent extractions. We also propose a new method for analysing extracted residues using the SEM-EDS that permits high resolution images of micro-residues, particularly starch and other fibres. We argue that, although both methods have limitations and instrumental challenges, when used in combination, provide a complementary means for documenting tool residues

An unusual, incised ground stone artefact from southwestern Victoria, Australia: its function and potential symbolic significance

An unusual, incised sandstone artefact recovered during an archaeological salvage program in Bannockburn, southwestern Victoria, has been uniformly ground and contains sets of regularly spaced, shallow grooves on either side. Microscopic study indicates that the grooves were incised with stone and used to sharpen or shape the edges of wooden implements. The wear outside the grooves indicates contact with soft wood or other plant material, possibly a soft plant bag. When compared with other examples that are similar, the regularity and distribution of the grooves suggest a symbolic meaning, perhaps tally marks or other form of communication

Food or fibercraft? Grinding stones and Aboriginal use of Triodia grass (spinifex)

Plant tissue and wooden objects are rare in the Australian archaeological record but distinctive stone tools such as grinding stones and ground-edge hatchets are relatively common, and they provide strong indirect evidence for plant food processing and woodworking, respectively. Ethnohistorical references to the Aboriginal use of stone tools for technologies related to fibercraft, basketry, hafting adhesives and fixative sealants (with gum, wax and resin) are also rare but all these tasks were probably more common than records indicate. Here we consider ethnohistorical evidence for stones in fibercraft and the processing of Triodia grass (spinifex) as a case study. We compare functional traces on experimental stones with traces on a museum specimen (CMAA 1926.591), which was collected ethnohistorically and reportedly used for \u27grinding spinifex leaves\u27. Residues and other traces on the museum specimen are consistent with both fiber-processing and seed grinding. We suggest that it may be difficult for usewear and residue analysis to determine if grinding stones were used to target Triodia spinifex for fiber, food or another particular plant product. Further experimental research is needed to refine criteria for identifying archaeological fiber-processing tools. However, we propose that the combination of traces previously interpreted as seed processing on bedrock grinding patches and portable grinding stones may also indicate the processing of Triodia spinifex for fiber

How a stone wedged in a gum tree shows the resilience of Aboriginal culture in Australia

Trees marked by Aboriginal cultural practices are a distinctive part of the Australian landscape. A recent discovery on Wiradjuri country in New South Wales shows some of these “culturally modified trees” may be much younger than anybody thought..