The use of bone surface modifications to model hominid lifeways 8i CHAPTER 3 The use of bone surface modifications to model hominid lifeways during the Oldowan Charles P. Egeland Ever since the ground-breaking taphonomic work of Bunn (1981) and Potts (Potts and Shipman, 1981) documented cut marks on bones from early Pleistocene deposits at Olduvai Gorge and Koobi Fora, bone surface mod- ifications have played an increasingly prominent role in understanding the formation of Oldowan faunal assemblages. The analysis of surface modi- fications, which include most prominently hominid butchery (cut marks, percussion marks) and carnivore (tooth marks) damage, can address many important issues in Oldowan archaeology, including (1) Which carcass resources did Oldowan hominids exploit? (2) How often did they obtain carcasses? (3) When they did acquire carcasses, did hominids have their choice of resources, or was the menu limited to what was available after other carnivores had had their fill? ( 4 ) What was the nature of the inter- action between hominids, as a relatively new member of the large car- nivore guild, and Plio-Pleistocene carnivores? These questions, and thus the analysis of bone surface modifications, must he integrated into any model that seeks to shed light on the socioeconomic function of Oldowan sites. The role of bone surface modifications in understanding faunal assemblage formation The process of faunal assemblage formation can be usefully understood in three distinct, albeit interdependent, components (Egeland et al., 2004: 3 4 5)• The first is carcass acquisition. This involves gaining access to a carcass regardless of the mode of that access (e.g., hunting or scavenging) or the nutritional condition of the carcass (e.g., fresh or desiccated). The second is carcass accumulation. Here, a carcass or carcass part is transported to and eventually deposited at a particular locale on the landscape. The third component is carcass modification, which occurs when bones or parts thereof are broken or partially/wholly destroyed. It is during this last process that bone surface modifications are created. Two important points must be made here. First, carcass modification, and thus the infliction of bone surface modifications, can occur at any stage of assemblage formation. Second, the modification component of assemblage formation is the most directly inferred because bone surface modifications provide one of the few unambiguous taphonomic indicators of hominid and carnivore involvement with bones (assuming, of course, that they can be correctly identified; see discussion later). What flows from this is the realization that the formation of a faunal assemblage, be it Oldowan or Neolithic, simply cannot be addressed with any rigor without the analysis of bone surface modifications. The role of actualism in identifying and interpreting bone surface modifications The perspectives offered in this chapter are all guided by actualism, which involves "observing present-day events and their effects in order to give meaning to the prehistoric record" (Gifford, 1981: 367; see also Simpson, 19 7 0; Lyman, 199 4 : 46-69; Pobiner and Braun, 2005a). Because it provides unambiguous linkages between traces (e.g., a mark on a bone), causal agen- cies (e.g., a stone tool slicing a bone), effectors (e.g., a sharp-edged flake), and actors (e.g., a hominid wielding a stone tool; terminology follows Gifford-Gonzalez, 19 9 1), actualism, and the uniformitarian assumptions that accompany it, provide the critical referential framework for under- standing past processes. Marean (1995) has provided a useful distinction between naturalistic and experimental actualism. Experimental studies directly control the variables that produce the observed traces, as in studies that purposely vary tool raw material to examine differences in cut-mark frequencies between, for example, obsidian and flint Hakes (Dewbury and Russel, 2007). Naturalistic research observes actors and their resultant traces but does not intentionally manipulate the variables. An excellent example of this form of actualism is found in Blumenschine's (1986) observations on the natural sequence by which carnivores in the Serengeti ecosystem consume different carcass parts. As we will see, actualistic studies, both experimental and naturalistic, play a central role in reconstructions of hominid butchery behavior and hominid/carnivore interactions in the Oldowan. So