mesolithic

5.2.6 Site investigation

Until recently, geophysical survey and remote sensing were not used routinely for the detection and investigation of Mesolithic sites and features (but see Marshall in Mithen 2000 for use of resistivity at Staosnaig Mesolithic site). The Scottish Mesolithic Geophysical Survey Project was established in 2002 by the Department of Archaeology at Glasgow University, in order to research the application of geophysical survey techniques to Mesolithic archaeology, and sites with different topographic and pedological characteristics were used as case studies. Geophysical survey has also been used as a general prospecting tool as part of the Inner Hebrides Mesolithic Project led by Steven Mithen. With the exception of Sand, Applecross, Highland, the results of these surveys have not yet been published in detail. At Sand a fluxgate gradiometer survey was undertaken of an area c. 500m2 directly in front of the rockshelter, with the primary objective of exploring the geophysical response of the shell midden deposit and establishing its extent. A sampling interval of 0.25m was adopted and the instrumentation was set to detect features up to 1m below the ground surface. The magnetic anomalies detected could be linked mainly to geological features, metal objects in the soil, or recent disturbances of the site, but no clear magnetic response was obtained from the midden deposit (Finlay 2009).

Archaeological geoprospection has seen limited application in Scotland, but has proved useful elsewhere (Carey et al. 2007).

Table 3 lists some common science-based techniques and the extent of their use in Scottish Mesolithic studies. With the exception of radiocarbon dating, there have been relatively few applications of these techniques. This is further highlighted by a survey of papers with a specific focus on the Scottish Mesolithic published in the Journal of Archaeological Science between 1975 and 2010 (Table 4). If archaeobotanical, archaeozoological, geoarchaeological, and palynological studies are excluded, which fall more within the realm of environmental archaeology, only three papers published in the Journal of Archaeological Science over the past 35 years are concerned with the scientific analysis of archaeological materials from Scottish Mesolithic sites. While the Journal of Archaeological Science does not represent the total picture, it is probably a fair reflection of past and present trends in Scottish Mesolithic research and highlights both the paucity of science-based research and the imbalance between environmental archaeology and archaeometry in what little research has been undertaken. While the lack of human remains from Mesolithic sites in Scotland probably accounts for the dearth of archaeogenetic research and stable isotope studies of diet and population movements, it is more difficult to explain why there have been so few applications of archaeometric techniques to the study of artefacts and ecofacts. One reason perhaps is the lack of specialist degrees in archaeological science at postgraduate (Master and PhD) level in Scottish Universities. Therein lie objectives and opportunities for the future.

Table 3: Applications of archaeometric techniques in Scottish Mesolithic studies

Area of Investigation Technique Applications
ISOTOPIC DATING Radiocarbon Numerous
NON-ISOTOPIC DATING Luminescence Bolsay Farm (Islay), West Voe (Shetland)
STABLE ISOPTOPES Dietary tracing Oronsay
Population movements Seasonality (molluscs, fish)
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ARCHAEOGENETICS aDNA check doc
ARTEFACT STUDIES Lithic use-wear Bolsay Farm, Gleann Mor (Islay), Smittons, Starr (Dumfries and Galloway)
Bone use-wear 'Obanian' shell middens, bevel-ended tools
Residue analysis Sand (Applecross) bevel-ended tools
Trace element provenancing Pitchstone sources (Arran)
SITE INVESTIGATIONS Remote sensing and geophysical survey Sand, Applecross, Newton (Islay), Port Lobh (Colonsay), Tiree, East Barns (East Lothian)

Table 4: Articles with a focus on the Scottish Mesolithic, published in the Journal of Archaeological Science between 1975 and 2010

Methodological emphasis No. of articles J Arch Sci ref.
Archaeobotany 1 vol 28(3), 2001: 223-34 (S Mithen et al.)
Archaeozoology 1 vol 34(3), 2007: 463-84 (E.H. Fairnell, J. Barrett)
Geoarchaeology 1 vol 17(5), 1990: 509-12 (A.G. Dawson et al.)
Geochemical fingerprinting 1 vol 11(1), 1984: 1-34 (O. Williams Thorpe, R.S. Thorpe)
Growth-line analysis of shells 1 vol 10(5), 1983: 423-40 (M.R. Deith)
Palynology 4 vol 11(1), 1984: 71-80 (K. Edwards, K. Hirons);
vol 16(1), 1989: 27-45 (A.H. Powers et al.);
vol 32(3), 2005: 435-49 (K. Edwards et al.);
vol 32(12), 2005: 1741-56 (K. Edwards et al.)
Radiocarbon 1 vol 37(4), 2010: 866-70 (M. Collard et al.)
Stable isotopes 2 vol 13(1), 1986: 61-78 (M. Deith); vol 26(6), 1999: 717-22 (M.P. Richards, R.E.M. Hedges)
Total 12 %nbsp;

5.2.5 Environmental reconstruction

A wide variety of scientific methods to reconstruct local and regional environments for Mesolithic sites are now available for use by archaeologists concerned with Mesolithic settlement in Scotland. These include the following:

Palynology and microscopic charcoal

Pollen analysis is the most widespread method for palaeoenvironmental reconstruction in Mesolithic Scotland applied to both off-site deposits and those from within culturally-rich sediments. The methods of palynology are well established and do not require any description in this report (the reader is recommended to consult Moore et al. 1991). Pollen analysis is most ideally undertaken in the context of a multi-proxy analysis of a sediment core in which the following are also examined: testate amoeba (which provide a measurement of wetness of bog surfaces); coleoptera (beetle remains used to reconstruct ecology and climate); chironimids (head capsules of aquatic larvae which are sensitive to environmental change); tephra (see above) and microscopic charcoal (which provides a measure of either human activity or natural fire events). Important applications of such methods relating to Early to Late-Mesolithic settlement can be found in Edwards et al. (2007) and Anderson (1998).

Plant macros

Plant macroscopic remains can be extracted either from off-site sediments cores or from culturally-rich deposits on archaeological sites. This term covers a wide range of remains including seeds, fruits, buds, scales, parenchymatous tissue, and wood charcoal. Where preserved on sites, macro remains can be hugely informative and help to offer a potential corrective to the view of Palaeolithic and Mesolithic people as primarily hunters and fishers (see papers in Mason and Hather 2002). The analysis of such remains from archaeological deposits often poses a considerable taphonomic question as to whether such remains derive from human activity or are naturally present within the deposits. Ideally they can provide a profile of the types of vegetation that have been growing locally and in some circumstances indicate the seasonality of occupation. The most abundant type of plant macro remains are fragments of charred hazelnut shell, as found in substantial quantities at Staosnaig, Colonsay, along with the remains of apple, lesser celandine, and a wide range of parenchymatous tissue. Wood charcoal can be indentified in some cases to species by identifying anatomical characteristics such as cell and tissue structure and vessel arrangement. The comparison between a vegetation profile produced from on-site wood charcoal assemblage with that from off-site pollen analysis facilitates the interpretation of each source of data, as undertaken at Bolsay and the adjacent Loch a'Bhogaidh, Islay (Kaminski in Mithen et al. 2000; Sugden and Edwards 2000).

Phytoliths

Phytoliths are siliceous precipitates that form within plant cells. Their morphology can be indicative of the type of cell and in some cases the type of plant within which they have formed. Because they are made of silica they are prone to survive under the right environmental pH conditions within sediments after the organic plant material has decayed.  Phytoliths are not preserved under extremes of pH and are subject to post-depositional taphonomic processes that can lead to fragmentation and constrain identification. Although phytolith studies have now become widespread in environmental archaeology and have considerable potential in the study of hunter-gatherer plant use, especially in regions where organic material rarely survives, there have as yet been no significant applications in the Mesolithic of Scotland.

Diatoms

Diatoms are a type of algae with cell walls made of silica. They are especially useful for archaeologists interested in past sea-level change because of three characteristics. First, each species of diatom has an ecological preference: some live in salt water, some in brackish water and some in fresh water. Second, each species has a unique type of cell wall and hence can be readily identified microscopically. Third, because the cell walls are made of silica they are relatively durable. Diatoms can be extracted from either off-site sediments being analysed to reconstruct sea-level change e.g. Dawson and Dawson (2000) or from on-site sediments when exploring local environments and post-depositional history.

Fauna

As with pollen the techniques involved in archaeological faunal analysis (encompassing terrestrial and marine fauna including fish) are well covered elsehwere and do not need to be rehearsed here (see Lyman 1994; Hillson 1998; Yalden 1999). With regards to Palaeolithic and Mesolithic Scotland the key questions that need to be addressed concerning the composition of the fauna through time, the range of wild animals being hunted and their relative importance, the seasons in which they are being exploited, patterns of butchery and carcass discard, and utilization with regard to food and raw materials. Symbolic associations with animals need to be taken into account but the manner in which these may influence a faunal assemblage will inevitably remain unclear. The key constraint for Mesolithic Scotland is simply the availability of fauna to analyse with the only significant published assemblages coming from the Oronsay middens and Sand. As with the study of plant remains the analysis of on-site animal fauna can inform about the Mesolithic economy and the environment within which the hunting and gathering were taking place. See also the ScARF Science panel sections: Archaeoentomology in Scotland and Palaeoclimatology.

Mollusc analysis

This is another area of environmental reconstruction in which methodology is already well-established (Claassen 1998; Evans 1972). The analysis of molluscs and crustacea, and other materials often found in association such as sea-weed, can inform amongst other things about the dietary preferences of Mesolithic people along with their particular patterns of coastal exploitation e.g. Deith (1983; 1986). Attention is paid to the species diversity found within an assemblage of shells together with the morphology of shells such as limpets and growth-line analysis, which can indicate the season of exploitation. It is also possible to analyse the oxygen isotopes within mollusc shells to gain an estimate of past sea temperatures. Cowrie shells in particular were used by Mesolithic peoples for beads (Mellars 1987; Simpson 1996), but it can on occasion be difficult to distinguish deliberate rather than natural perforations on shells (Saville 2004c, n.6).

Sediment analysis

A wide range of physical and geochemical techniques are available to analyse sediments coming from Mesolithic archaeological sites. Micromorphological analysis is now routinely used in a wide range of periods (Courty et al. 1989), but is yet to receive appropriate application in Mesolithic Scotland even though this could address pervasive problems of site formation. Particle size analysis, loss-on-ignition, magnetic susceptibility, and x-ray techniques are all routine methods for characterising archaeological sediments and should be widely applied for studying Mesolithic sites in Scotland.