The relevance of basic science to stone tool use and meat eating: standardisation of bone surface modification methods and interpretations

Abstract

Modifications to the surfaces of fossil bones are one of the most important lines of evidencefor understanding different issues in palaeoanthropological, archaeological, and taphonomicresearch. Bone surface modifications (BSM) are used to infer past lifeways and behavioursthrough site formation processes, subsistence patterns and adaptations and how theyinfluenced human evolution, as well as patterns of economic and social evolutions. The studyof BSM first appeared in palaeontology in the mid-19th Century, before gaining traction inarchaeology during the processual boom of the 1960s. By identifying BSM fromethnographic studies of BSM created by people in the present day and comparing them tomarks found in the archaeological record, archaeologists were able to tie traces to specificbone modifying actions (e.g. Binford 1978; Brain 1981; White 1954). However, traces left bynon-human modifiers can mimic those produced by humans (e.g. Blumenschine et al. 1996;Olsen and Shipman 1988; Selvaggio 1994a; Shipman and Rose 1984). Experimentaltaphonomic studies in zooarchaeology have been largely conducted with the goal ofconfidently tying traces to known actors and effectors (Gifford-Gonzalez 1989b, 1991).However, variation in experimental design, experimental bone subjects, and how the resultantBSM are classified and analysed has contributed to a lack of consensus between researchers.For example, cut marked bones found in deposits dating to 3.39 million-years-ago (Ma)challenged the current paradigm that butchery, meat-eating behaviours and, subsequently,stone tool use were present in pre-Homo hominins (Dominguez-Rodrigo et al. 2011;McPherron et al. 2011). Furthermore, debates based on bone surface modificationinterpretations illustrate the lack of consensus amongst researchers about how to best identifyand differentiate anthropogenic from non-anthropogenic modifications on bones. In thecontext of the origins of tool-assisted butchery, having a robust method to identify thesetraces is a foremost concern for understanding our own evolution. Resolving this issuerequires two things: 1) a large dataset in which marks on bones have been producedexperimentally under highly controlled conditions; and 2) a replicable method forquantitatively analysing and describing traces on bone surfaces. This research providesimpetus for the standardisation of bone surface modification studies, specifically theexperimental and analytical methods, as well as how researchers identify and classifymodifications and, subsequently, communicate their results and interpretations.This thesis describes three datasets that examine how known variables influenced butcherymark morphology. The first dataset examined the effect of the most common methodsmtap water boiling, prolonged (gentle) simmering, laundry powder / liquid boiling, andmacerationmof experimental preparation on butchery mark morphology. The results indicatethat the most common method for cleaning experimental assemblages, tap water boiling, isthe most damaging process, with a high degree of variation between the before and afterassemblages. The least damaging process was cold water maceration; however, this methodalso displayed variation in some cut mark traits. The second dataset examined how force,velocity, and angle influence butchery mark morphology when controlled and manipulatedindependently with a mechanical arm. The results indicate that mechanically controlling theforce, velocity, and angle of percussion strikes has little influence on percussion markmorphology, while cut mark morphology was significantly influence when the same physicalvariables were mechanically controlled. Similarly, the third dataset also examines the effectsof these same physical variables on a controlled butchery assemblage and a freeformassemblage produced by six volunteer butchers. Both the controlled and freeform butcheryexperiments produced results consistent with the mechanically controlled dataset cut marks.No tested physical variable (angle, velocity, or force) could be directly and consistently tiedto specific attributes of percussion mark morphology, which suggests that percussion markmorphology may be affected by alternate variables, such as effector morphology. Cut marktraits, however, were consistently and directly tied to the physical variables undermanipulation, to the extent that cutting, slicing, and scraping marks can be differentiated.These results indicate that butchery mark morphology is influenced by different physicalvariables and that by understanding how they are influenced the archaeological record can bemore confidently interpreted.