palaeolithic

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.

5.2.4 DNA and the Mesolithic in Scotland

The last decade has seen a significant increase in the use of genetic analysis in order to reconstruct past population movements. This includes analyses based on both modern and ancient DNA. aDNA (ancient DNA) work is very unusual in Mesolithic contexts in Britain, Brian Sykes’ work with Cheddar Man is the most widely known but the recent reconstruction of the complete genome of a Mesolithic auroch from Derbyshire should be noted (Edwards et al. 2010). In the absence of aDNA the use of genetic analyses of modern populations is used in order to reconstruct past histories. This can include some very specific claims about the Mesolithic past and about the Mesolithic-Neolithic transition in the British Isles. For example, on the basis of modern population samples Sykes argues that ‘the Y-chronosonal evidence suggests that Mesolithic immigrants from Iberia went mainly to the western and southern British Isles, contributing initially about 24% of modern lines, which is rather similar to the maternal figure’ (Oppenheimer 2006, 152). Sykes argues for a clear distinction on genetic grounds for colonisation routes into eastern and western Scotland – the former ultimately deriving from the Balkans and the later from Iberia. Sykes reports that the Hebridean islands include high proportions of ‘clans’ (groups of related genetic sequences) ‘Jasmine and Tara’ that directly relate to the Neolithic expansion of agriculture, with these sequences in Scotland indicating population movement along the Atlantic fringes of Europe (Sykes 2006, 212). Whilst the frequencies of the Katrine ‘clan’, ultimately deriving from northern Italy c. 15000 years ago (an Alpine LGM refugia) are higher in Lewis than anywhere else in Scotland. Recent claims about the Mesolithic-Neolithic transition in Ireland are even more specific: ?About 13% of Irish mtDNAs belong to putative Neolithic clusters … there is an even distribution of putatively Neolithic haplogroups around the island, suggesting that females who arrived after the initial settlement were not restricted to east-facing regions. By contrast, however, Y-chromosome lineages of putative Near Eastern Neolithic origin … appear to be virtually absent from the west of Ireland’ (McEvoy et al. 2004, 695).

The use of modern populations to reconstruct past histories has been criticised on a number of grounds, including sample sizes and a failure to consider more recent histories of migration (for discussions of the relationships between archaeology and genetics in the specific context of early Holocene history see Pluciennik 2006; Thomas 2006). However, academic critiques have not significantly held back sales of popular books which offer a sense of antiquity and ancestry (for discussion see Nash 2007). The popular presentation of Cheddar Man’s supposed direct descendant, a school teacher from Cheddar, is indicative of the ways in which ancestry and senses of belonging are entangled with the reconstruction of genetic family trees.

The incorporation of genetics into anthropology and archaeology in general has been transformative (Pálsson 2007) and creates new possibilities. The resulting narratives sometimes feel unfamiliar and challenging. There can be a significant disconnect between those who use genetic data and those who do not, and at times, a sense that archaeologists feel that if they ignore the genetic interpretations the latter will fade away. Integrating the two sets of data is not straightforward but it is essential that Scottish archaeological research into the Mesolithic period actively engages with the interpretations offered by genetic research.   Recent genetic and isotopic work offers much more than straightforward detail of past migrations and will, it is to be hoped, be integrated into studies of early Prehistory in Scotland.