What makes bones shiny? Investigating trampling as a cause of bone abrasion

Taphonomic modifications on animal bones have the potential to provide a wealth of information on the depositional histories of faunal assemblages. However, certain modifications have received little attention and their interpretation remains complex due to their varied or uncertain aetiology. This has hindered progress in approaches to taphonomic research and it remains relatively rare that a comprehensive suite of modifications is recorded during zooarchaeological analysis. Abrasion, defined as a shine or polish on bone, is one such modification, with a plethora of processes having been cited as a potential cause. Relatively little holistic analysis of archaeological specimens has been carried out and consequently the interpretative potential of the modification is yet to be realised. This paper examines the degree to which the process of trampling causes bone abrasion. Trampling causes multiple, sub-parallel, linear striations on bones and has been suggested by some researchers as a cause of abrasion (see Andrews and Cook, Man 20:675-691, 1985; Behrensmeyer et al., Palaeogeogr Palaeocol 63:183-199, 1986; Fiorillo, Univ Wyoming Contrib Geol 26:57-97, 1989; Myers et al., Am Antiquity 45:483-490, 1980; Nielsen, Am Antiquity 56:483-503, 1991; Olsen and Shipman, J Archaeol Sci 15:535-553, 1988). Research presented here involves statistical analysis of a large and diverse faunal dataset from seven British sites. Results from both correlation and logistic regression analysis demonstrate the very close relationship between the two modifications, although this is not the case at every site. These findings strongly suggest that trampling is a major cause of abrasion in a British context. Once the relationship is established at a specific site, the modification can be more reliably used for reconstructing the taphonomic trajectory of an assemblage.