A twist in the tail: on the validity and characteristics of the Phase III handaxe assemblage from Barnfield Pit, Swanscombe, UK

The Lower Palaeolithic site of Barnfield Pit, Swanscombe, UK, is famous for its extensive geological sequence that represents the whole of the Marine Isotope Stage (MIS) 11 (Hoxnian) interglacial. Its archaeology records a change in stone tool manufacture within the MIS 11c substage, from a Clactonian core and flake assemblage in the earliest part of the sequence (Phase I) to an abundance of Acheulean handaxes of pointed form in the Middle Gravels (Phase II). The Phase III deposits, particularly the Upper Loam, correlated with MIS 11a, have long been claimed to contain a further shift in the Acheulean tool forms, from a point dominated to an ovate dominated handaxe tradition that features tools with twisted edges. Here, we explore the character and validity of the Phase III assemblage from Barnfield Pit, combining a three-dimensional geometric morphometric approach to the study of handaxe shape alongside qualitative measures of post depositional processes. Our results demonstrate that the Phase III deposits contain an assemblage that is morphologically distinct from that within the Phase II Middle Gravels and comparable to those from laterally equivalent MIS 11a sites on Dartford Heath. At the same time, we highlight the complexity of the archaeology within the upper deposits at Barnfield Pit and suggest that the change in normative approaches to tool manufacture that is observed within the Lower Thames Valley between MIS 11c and MIS 11a may occur earlier than previously thought. This presents significant implications for our understanding of hominin social upheaval in response to global climatic cooling across Britain and northwestern Europe.