Deserted Britain: Declining Populations in the British Late Middle Pleistocene
Ashton, Nick, Lewis, Simon, Antiquity
Until the 1970s there was thought to be a semi-continuous population in Britain from the earliest human occupation (e.g. Smith 1894; 7; Evans 1897; 697-8; Paterson 1941: 408; Wymer 1968: 308-12). Since then, adoption of the oxygen isotope sequence, and refinements in biostratigraphy and dating, have suggested that humans were present in Britain from at least Oxygen Isotope Stage (OIS) 13 (Roberts et al. 1995), but that there was a possible absence during the last interglacial (OIS 5e) (Stuart 1976; Currant 1986; Wymer 1988). This has been based on the apparent lack of artefacts associated with faunal assemblages that include hippopotamus, a marker species for the last interglacial (Sutcliffe 1975; Stuart 1976). More recently it has been suggested that this absence may have extended throughout OIS 5 and into 4 (Currant & Jacobi 2001) and possibly from OIS 6 (Jacobi et al. 1998; Ashton in press). Here we look at the problem afresh, with particular reference to evidence from the Middle Thames Valley.
Problems and methods
Assessments of Palaeolithic population levels are problematic, particularly due to the variable preservation of artefact-bearing deposits. Further problems arise from the variable intensity of fieldwork. Equally, the interpretation of individual sites in terms of population is rarely straightforward; a thousand artefacts might represent occasional discard over several thousand years, or simply an afternoon's knapping.
Some of these problems may be circumvented by examining fluvial terrace aggradations, where any artefacts within the terrace unit represent a variety of activities from a broad area over a defined length of time (cf Hosfield 1999). Each terrace unit can be compared to younger or older units, providing a mechanism for assessing change in artefact numbers through time. The problem of variable preservation of sedimentary units is overcome through mapping of the terraces, and collector bias is reduced through selection of part of a single river system. Finally, use of this method removes the problems of interpreting the length of time represented by individual assemblages.
The Middle Thames Valley is a good area to test the method; it has a rich history of collecting and fieldwork, with numerous sites and find-spots, while the terraces are well mapped and their chronology is well constrained (Bridgland 1994; TABLE 1; FIGURE 1). The artefacts from these terrace aggradations are, in the majority of cases, derived, and must be interpreted with care. States of condition vary from little or no edge abrasion to rolled. It is assumed, though, that in most cases artefacts originate from sedimentary units that are only slightly older than the gravels into which they have been incorporated. In theory, much older artefacts could be reworked into younger terrace aggradations, increasing artefact numbers in the lower terraces. The suggestion being tested is that population decreases through time, making any decrease in artefact numbers more significant if artefacts have been reworked from higher terraces.
[FIGURE 1 OMITTED]
Many factors affect the rate and type of recovery. The majority of artefacts from the Middle Thames were collected (not excavated) by individuals who in many cases either recovered the artefacts from active gravel pits (e.g. Brown 1887) or otherwise from trenches for house foundations (Smith 1894). This type of collecting was important from the 1890s until the start of mechanised digging in the 1930s. The timing of gravel-pit development and of urbanization have therefore had an important impact on artefact recovery.
Unfortunately different artefact types have been selectively recovered, with flakes and cores kept by some collectors, but not by others. Bifaces, however, were more easily recognized and universally collected, providing therefore a better reflection of artefact densities within the study area. …