PHYSICS

This paper serves as an introduction and discussion of a collection of five papers originally presented in a symposium held at the 69th meeting of the Society for American Archaeology in 2004 entitled "Applied actualism: Experimental studies of hominid activity traces". These papers primarily present actualistic studies aimed at addressing questions of hominin carcass processing activities, generally using cutmark data. They serve as a reminder of the utility and importance of actualistic studies to test hypotheses of hominin behavior using zooarchaeological and taphonomic data. We review the manner in which actualism is used in these various studies of human butchery practices to construct models to generate test implications for the archaeological record. Finally, some considerations for future actualistic work are discussed.

The frequencies of surface modification such as percussion, cut, and tooth marks on experimental faunal assemblages are not always directly comparable to those in fossil assemblages. Extensive post-depositional modification of bone surfaces may render many of these marks unidentifiable, depressing the overall frequencies or affecting some mark classes more than others. An analysis of the fauna from an open-air Middle Stone Age site on the Loiyangalani River in the Serengeti Plain, Tanzania, illustrates this point. A coding system is presented here that allows the elimination of heavily affected fragments from analysis so that the observed mark frequencies can more closely approximate their original ones.

Cutmarks are the most direct evidence of faunal butchery by humans. However, the physical properties of the creation of cutmarks are currently poorly understood. Experiments to quantify the minimum amount of force required to cut through muscle tissue and to produce a visible cutmark on the surface of bone were conducted. Those force values were then correlated with the maximum amount of force exerted by a human butchering with a stone tool. By quantifying such data, archaeologists can better understand the conditions conducive to creating cutmarks. Results show: 1) less force is required to cut through soft tissue when using obsidian as opposed to chert flakes; 2) the average depth of a visible cutmark is 65-80 mm; and 3) on average males can exert a greater maximum force using both large and small stone tools than females, but both can exert forces that far exceed the minimum force requirements tested in this experiment. These results present compelling data regarding the physical processes and agents involved in the formation of a cutmark on a bone, and offer incentive for future studies to be conducted.

Cutmark frequencies are often cited in discussions of Oldowan hominid behavior, yet their interpretation remains enigmatic. To strengthen inferences derived from cutmark data, we conducted experiments with Turkana butchers. We test two hypotheses: (1) cutmark frequency is related to the amount of meat present, and (2) cutmark frequency is related to the size of the bone/carcass being butchered. Hypothesis 1 is not supported, while hypothesis 2 is supported. We document a positive correlation between bone/carcass size and cutmark frequency. We therefore advocate treating bones/carcasses of different sizes as analytically discrete units.

Studies of cut marks have long been the subject of controversy regarding their ability to infer hominid carcass exploitation behavior, and the interaction between hominids and carnivores. Previous studies have emphasized the usefulness of cut mark frequency and distribution to reconstruct hominid access to carcasses. Still, one pending issue is how cut mark patterns vary between different carcass sizes (small versus large). This work presents new experimental results in which cut marks on small-sized carcasses are analysed and compared to both 1) experimental samples with larger-sized animals, and 2) the FLK 22 (Zinj) Plio-Pleistocene archaeological site.

The butchery and bone transport behavior of Plio-Pleistocene hominids has sparked much debate among paleoanthropologists because of the implications these behaviors have for hominid site use and socio-ecology. Contemporary hunter-gatherers provide useful test cases for zooarchaeologists interested in modeling these behaviors prehistorically. Among the set of available utility indices meant to aid in predictions of carcass resource use, return rates may be the most useful, as they estimate the net gain associated with nutrient extraction. This study presents experimentally-derived post encounter return rates associated with the butchery of meat-bearing appendicular skeletal elements from Size Class 2, 3 and 4 ungulates. Combining these new data with published data on marrow extraction allows composite return rates to be calculated. This study applies these data to ethnoarchaeological reports of bone transport among Hadza (Tanzania) and Kua (Botswana) hunter-gatherers. Results indicate that return rate does not systematically correlate with appendicular bone transport among contemporary foragers, suggesting: (1) the difference between zooarchaeologically-meaningful (i.e. individual skeletal elements and element portions) and behaviorally-meaningful (i.e. articulated limb segments) units of analysis exaggerate the differential transport potentials of these skeletal elements and (2) maximizing caloric gain per unit time at the site of carcass acquisition may not be a primary goal. Return rates also do not significantly correlate with skeletal part abundances from a number of important Plio-Pleistocene sites. This in turn suggests that current return rate data are probably not comprehensive enough to adequately account for the many variables influencing transport decisions. Given these findings, we suggest that return rates may be more productively applied to questions of carcass processing instead of carcass transport. Addressing these questions requires an analytical shift from skeletal part abundances to hominid-inflicted bone damage. We therefore integrate experimental return rates with data on surface modifications from some Plio-Pleistocene assemblages and examine the implications for hominid carcass processing and site use.