The most recent review of the chronology of the Early Mesolithic (Reynier 2005) listed just 20 radiocarbon measurements from 10 sites that were judged to be reliable. The vast majority of systematic dating work on the Mesolithic was undertaken in the 1970s by Switsur and Jacobi (1975; 1979). At this time the large sample size required for conventional radiocarbon dating meant that many pieces of bone or charcoal had to be bulked together for analysis, perforce leading to the amalgamation of material of potentially differing ages in a dated sample. This meant that the resulting radiocarbon date would be an average of the dates of all the fragments of material in the sample and potentially reflect the actual age of none of them. Similarly, the large amount of material needed for dating meant that in practice there was rarely any sample choice, simply those few samples of organic material that were large enough had to be submitted for radiocarbon dating. This led to many radiocarbon measurements that have poor or uncertain links with archaeological events. At this time charcoal samples were often not identified to age and species before submission for dating and, even when this was done, charcoal from tree species that might be several hundred years old when cut down was dated; an old-wood offset of a few hundred years was not considered significant within the precision that could then be produced by radiocarbon dating. In consequence, a large proportion of legacy dates from Mesolithic samples represent termini post quos (hereafter TPQs).
This array of problems, coupled with the difficulty of dating bone this ancient, means that even key sites can be poorly dated: Thatcham III, the pre-eminent early Mesolithic site in Southern England, a palimpsest of repeated occupations, is represented by a single precise radiocarbon date, with the remaining three measurements on bulked material providing only TPQs at best (Table 1). In sharp contrast, Star Carr, following recent work, now has 223 associated radiocarbon dates (Milner et al. in press, tables 17.1–17.3). This compares with just 123 measurements for all other typologically and/or securely dated Early Mesolithic sites, many of which come from just a few sites, such as Thatcham V (12 measurements) (Reynier 2005; Conneller and Higham 2015), Aveline's Hole (23 measurements) (Schulting 2005, tables 11–12 and fig. 37), Worm's Head Cave (7 measurements on four samples) (Meiklejohn et al. 2011) and Cramond (6 measurements) (Lawson 2001). This situation is depressing, but is slowly improving: recent excavations have been able to take advantage of new techniques of radiocarbon pre-treatment and analysis, and focused dating by Accelerator Mass Spectrometry (AMS) on human bone (Meiklejohn et al. 2011) and bone and antler tools (Bonsall and Smith 1990; Elliott 2013) has revealed the potential for obtaining new evidence from old collections; a similar project is urgently needed to improve dating of settlements.
New dating programmes will take us only so far though: the vast majority of Mesolithic sites lack organic remains suitable for dating. Away from caves or middens or wetlands, such as river floodplains and infilled lake basins, faunal remains are not preserved. Beyond these areas, we are dependent on the relatively rare preservation and excavation of sealed contexts such as pits and hearth-pits with charred hazelnuts or charcoal from relatively short-lived species. For entire regions of Britain, a combination of geomorphology and historic and current land-use mean that datable samples will be rare or even absent. For these sites and regions, we will always need to rely heavily on typochronological schemes. It is unfortunate that these are less refined in Britain than on the Continent; however, the situation is rather better for the early Mesolithic than the late.
Work on the early Mesolithic over the past century has identified considerable variation in microlith forms. Clark (1934) was the first to point out the distinctive basally modified forms found in the area around Horsham. Radley and Mellars (1964) built on earlier observations by Francis Buckley to suggest two main types of early Mesolithic industries in northern England. 'Star Carr' and 'Deepcar' types were distinguished by differences in microlith form and raw material usage. Subsequent work has highlighted that these two types extend across England and Wales (Jacobi 1978; Reynier 2005). More recently the distinctive Midlands assemblages with inversely retouched Honey Hill forms have been defined (Saville 1981). While Jacobi (e.g. 1981) saw variation over time in these groupings, a systematic survey and analysis by Reynier (1998; 2005) has had the effect of formalising and stabilising these assemblage types. Reynier suggested each assemblage grouping was also characterised by different technologies, settlement patterns and hunting strategies. Reynier also believed differences in these assemblage types had a temporal component, with Star Carr type sites appearing first, around 9700 BP, followed by Deepcar types after 9400 BP, and finally Horsham from 9000 BP, though he suggested that, once established, these 'types' co-existed.
Advances in radiocarbon dating since Reynier's analysis in the late 1990s, not least the advent of a radiocarbon calibration curve covering this period (Stuiver et al. 1998; Reimer et al. 2013), mean that a new analysis of this material is now warranted, even though relatively few new sites with organic preservation have been excavated in the intervening years. In attempting to place Star Carr within its contemporary British context, we have created Bayesian models for the chronological range of three types of Mesolithic lithic assemblages, based on the occurrence of certain key microlith forms. These are: Star Carr-type assemblages, Deepcar types, and basally modified microlith assemblages. We have also modelled the chronological range of the preceding Terminal Upper Palaeolithic Long Blade assemblages, in order to understand their relationship with the earliest Mesolithic. Finally, we have modelled the start of late Mesolithic assemblages containing small scalene triangles, though the entire span of this microlith form is beyond the scope of this article. We note that these categories represent a considerable over-simplification of the nature of Mesolithic assemblage types. Microlith forms show regional differences and chronological change over time – for example, the appearance of curve-backed pieces in late Deepcar-type assemblages, such as Oakhanger V/VII and Marsh Benham (Jacobi 1981). It is also likely that each 'type' contains further possible divisions based on microlith form; however, this needs to be the subject of further detailed techno-typological research which is beyond the scope of this article.
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