S. de Juana’s research while affiliated with Complutense University of Madrid and other places

Current analogical data used to infer prehistoric human bone breakage rely on a plethora of experimental hammerstone-broken bovid bone sets. Several criteria have been argued to be diagnostic of bone breakage by humans, among which the most important are: a specific range of broken specimens bearing percussion marks, a specific distribution of different percussion mark types, metric properties of notches, differential notch type distribution, and the angle of oblique breakage planes. The present work shows that those properties derived from the breakage of bovid bones cannot be universally applied to all types of animals. As an example, here it is experimentally demonstrated that hammerstone-broken equid bones (with different thickness and structural properties compared to bovid bones) show different values in all these variables and some of them overlap with criteria documented in bones broken by static loading. This suggests that the agents of equid bone breakage are more difficult to identify, and that the number of variables that can be successfully used to that end is smaller than in bovid bones.

Recent experimental studies have developed new diagnostic criteria to differentiate between trampling and cut marks. Within cut marks, these diagnostic criteria have been useful to differentiate between marks made with simple and retouched flakes. The present study expands the application of these criteria using a multivariate analysis to discriminate marks created with handaxes from those made with stone tool flakes. A discriminant analysis resulted in a selection of specific variables, which can successfully differentiate cut marks made with handaxes from those created with retouched flakes in more than 80% of occasions. The utility of this analogical taphonomic signature created by handaxes is discussed in the light of their potential value as butchering tools.

Microscopic signatures have previously been used to emphasize the similarities of butchery and trampling marks. The experimental background applied to differentiate both types of marks has been rather limited and authors have sometimes reached conflicting conclusions. This is partly due to methodological reasons: some authors have used very high magnification to examine microscopic features, whereas others have relied on more reduced magnification. Likewise, some experiments have exposed bones to trampling for reduced periods (minutes) whereas others have used longer time periods (hours). The present study stresses that the use of a scanning electronic microscope is not practical for identifying the impact of butchery and trampling marks in complete bone assemblages. It also emphasizes that previous studies have not addressed all the possible variables that could potentially be used to discriminate these marks, nor have they quantified the morphological patterns of each type of mark. Here we present a multivariate analysis of more than a dozen variables and show that butchery and trampling marks have very distinctive microscopic morphology. We advocate the use of a low magnification approach (≤40×), which can enable the analysis of complete assemblages using either hand lenses or binocular lenses. We also show the morphological criteria that differentiate butchery cut marks made with simple and retouched tools. We show that whereas complete discrimination of marks is impossible due to some degree of overlap, the list of criteria derived through multivariate analyses can be confidently used to correctly differentiate butchery and trampling marks in more than 90% of cases.

Preliminary experiments on bone breakage have shown the potential utility of quantifying some of its diagnostic features (percussion marks, percussion notches) for taphonomic inferences about human and carnivore involvement in bone breakage in faunal assemblages. The present study increases the range of experiments undertaken to understand the identification of hammerstone percussion (dynamic loading) and its differences from carnivore bone breakage through tooth pressure (static loading). This study contributes to a better understanding of frequencies of percussion marks, uncovers and quantifies those percussion marks that lack key diagnostic features to be identifiable and that could be mistaken with carnivore tooth marks, quantifies notch types, shows different size ranges for notches on bones from small and large fauna than previously reported, quantifies the proportion of notches bearing percussion marks, and introduces new size data for percussion (impact) flakes and percussion marks. Furthermore, all these variables have been applied to a dual experimental set: one experiment using non-modified hammerstones and another based on the use of modified hammerstones. Results vary considerably according to hammerstone type. Some of these taphonomic variables increase the range of equifinality when identifying marks and notches created by different human and non-human agents. This calls for further caution when using isolated variables and features rather than a holistic approach to make taphonomic inferences.