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The overall aim of the TRACE project is to understand the range and variation of activities at a number of key wetland sites in Northwest Europe during the Mesolithic period by employing and refining techniques of microwear and residue analysis. Activity patterns are identified by investigating traditions of tool technology, function and ideology.

A number of Mesolithic wetland sites in Europe contain organic artefacts that otherwise would have perished in dryland environments. Focusing on wetland sites enables a fuller picture of the material and functional diversity of hunter-gatherer toolkits to be accessed. Yet, despite this potential, research of Mesolithic wetland sites often prioritises the economic benefits of these environments for hunter-gatherers. Meaning that, previous to this project, a limited amount of research has concentrated on the technology and range of tasks performed here, especially non-food procurement craft based activities. Indeed, emphasis has largely been on the attractiveness of wetlands for fishing, irrespective of whether empirical evidence for fishing activities exists within the archaeological record. As a result, less attention has been paid to the importance of plants in hunter-gatherer diets and craftwork; the social and ideological role of stone and organic tools for wetland hunter-gatherer communities is another area of research that has received less consideration. The Trace project aims to use the scientific methods of microwear, and to a lesser degree, residue analysis to address these core gaps in our understanding of Mesolithic wetland communities in Northwest Europe.

TRACE has selected and analysed tools from Ireland, the United Kingdom and the Netherlands. The tools analysed by TRACE range in date from 7530-4000 cal BC. It was of scientific interest to include flint and chert and organic tools in order to compare the development, distribution and topographic features of microwear traces between these stone types.

The TRACE Project achieved each of the objectives it set out to achieve. One of the primary objectives aimed to establish scientific evidence for the range of tasks undertaken in wetland contexts. A key aspect of this research was investigating microwear evidence for fishing activities in relation to plant-based tasks. Microwear analysis results demonstrated that it was possible to identify tools that had been utilised for fish processing when present within an assemblage. This was not dependent on raw material as fish processing traces were clearly identified on flint (Dutch) and chert (Irish) tools.

Of particular significance, was the quantity of transverse siliceous wild plant working traces on regular /un-retouched blade forms from the Dutch sites of Hardinxveld Polderweg and De Bruin: indicating a high level of plant craftwork was being carried out by these Mesolithic communities. Research on this ubiquitous yet enigmatic plant polish is ongoing, and an article co-authored by the fellow and Scientist in Charge is currently in prep (see below). One of the main outcomes of this body of research has been establishing a spatial and chronological pattern to the occurrence of this particular type of polish: originating in the Early Mesolithic, more commonly occurring in the Later Mesolithic, and continuing until the Middle Neolithic when it abruptly disappears from the archaeological record. Comparable traces exist in other regions of Northwest Europe, with some variation on tool morphology (i.e. the Dutch blades are un-modified, Scandinavian and French blades are typically denticulated or ‘notched’), indicating a common tradition of craft production, which may be linked to subsistence practices. In the Netherlands, the continuity of this polish throughout the Mesolithic and early Neolithic indicates an ongoing tradition of craftwork which suddenly falls out of practice once local production of cereal crops takes hold in the Middle Neolithic. Thus it is likely that these plant traces are connected to a craft technology which in turn is linked to a food source, for example, fishing baskets. To this end, it was highly significant that during the course of this project comparable transverse siliceous plant-working traces were identified on chert tools from the Irish site of Clowanstown, where fishing baskets have also been recovered. Conversely, although just a small selection of tools were analysed from the British Mesolithic sites of Star Carr and Flixton (both located in the Vale of Pickering, Yorkshire) no plant traces were identified. Future research aims to investigate this connection between the occurrence of transverse siliceous plant polish on stone tools and fishing equipment further, and to understand why Star Carr – located at the lake edge - bucks this trend.

TRACE’s research on the variability in the relationship between tool form/function and curated/ expedient technology showed that hunter-gatherers were selecting certain tool types for specific tasks. In the case of the transverse siliceous plant polish discussed above, these wear traces nearly always occurred on regular un-retouched blade forms from the Dutch sites. However, in Irish Mesolithic wetland sites, these traces were identified on a broader range of tool forms. Despite being located in a comparable wetland environment, the blades analysed from Flixton and Star Carr had a very different function: principally butchery, antler and bone working tasks. Furthermore, microwear analysis of flint and chert tools from the platform at Clowanstown, County Meath, Ireland, has identified a ‘fishing toolkit’ – with polish relating primarily to fish processing, but also plant craftwork (see above discussion), conceivably connected to the manufacture of the fish traps that were recovered nearby. Analysis of a cache of flint flakes from this same platform revealed that just one tool had been used to process fish; the other two were un-used despite being of extremely high quality Antrim flint.

Overall, the question of curation remains a complex issue. One of the reasons for this is that siliceous plant polish forms very quickly; its highly visible, reflective, and can obscure other, more ephemeral traces, such as butchery. It is also more difficult to assess the duration of use, because of the speed in which it develops. To investigate whether the Irish chert tools were indeed being curated, and whether these tools display different types of microwear traces, TRACE used portable XRF analysis. The Irish chert assemblage was chosen for this particular study as prior research conducted by the Fellow has located the probable quarry source for the tools analysed, meaning that full chaîne opératoire: from procurement to use life, specifically questions of curation – the movement of chert in and around the Irish Midland region - and final deposition can be scientifically addressed. The combined data from the use-wear and XRF will be published in a co-authored paper (see below).

Microscopic techniques of microwear and basic-level recording of microresidues by the Trace Project has thrown new light on how recovery circumstances alter/reduce validity scope of use-wear on different materials. Analyses demonstrated that not only does coarser grained chert display microwear traces comparable to that identified on flint, its greater porosity may contribute to better preservation of microresidues, with residues becoming entrapped within the chert laminae. Conversely, preservation of microresidues at Star Carr has been shown to be more problematic due to the highly acidic peat deposits into which artefacts were deposited. A long-term (one-year) digenesis burial experiment, whereby flint and chert flakes have been used on a range of plant, animal and mineral substrates before being buried in low/high pH archaeological deposits at Star Carr is aiming to address this question of variability in raw material/microresidue preservation further.

An under-acknowledged aspect of hunter-gatherer wetland archaeology is the presence of absence for ritualised behaviour. TRACE used a high power free-arm metallurgical microscope to study wear traces on a large shale axe deposited into a cremation pit at the site of Hermitage, Co. Limerick, Ireland. This research has established ground-breaking evidence for symbolic treatment of this artefact beyond that inferred by its funerary context. Dating to the Early Mesolithic, the axe has been ‘decommissioned’ by intentionally blunting the cutting edge prior to deposition. Through microscopy, TRACE identified residues of probable cremated bone fragments and established that the axe surface displayed signs of heat alteration, which were not commensurate with deposition into the cremation pyre. It is likely that the axe was therefore blunted, before being placed directly onto the hot cremation deposit within the pit. This is a highly symbolic and personal act which throws new light on Mesolithic ritual and ideological behaviours which could only be fully revealed through microscopic analysis. The results of this research is being published in a paper co-authored by the fellow and Scientist-in-Charge.

The research carried out by the TRACE project has shown that it is possible to develop a methodological and interpretive framework for comparing and contrasting different Mesolithic wetland sites in Northwest Europe. Microscopic information recorded by TRACE has stimulated a range of ongoing research questions. The successful outcome of the TRACE analyses has led to the Fellow being employed as Research Associate on the ERC-funded POSTGLACIAL project (University of York). She is now applying the scientific methods of microwear and residue analysis learnt throughout the course of her Marie Curie to advance current understandings of the spatial and temporal distribution of activities at Star Carr: comparing the dry and wetland areas of the site. This model of scientific research on microscopic traces of tools from European hunter-gatherer wetland sites, which has led to the successful results discussed above, can now be considered best practice.

The TRACE project expanded the collaborative research network of Leiden University by strengthening pre-existing links to the United Kingdom (York and Manchester Universities) as well as Ireland (University College Dublin and the National Museum of Ireland). TRACE successfully demonstrated the potential for microscopic analysis of artefacts from wetland sites to reveal otherwise invisible information about subsistence and craft in the Mesolithic. Significantly, new insights into the symbolic treatment of stone tools (e.g. the deliberate blunting of the Hermitage axe) at a time for which we know very little about the complexity of human ideological and sociological behaviour, attests to the broader socio-economic impact of the TRACE project.