Differentiating between cutting actions on bone using 3D geometric morphometrics and Bayesian analyses with implications to human evolution

Studies of bone surface modifications or B-S-Ms (BSMs) such as cut marks are crucial to the understanding of human and earlier hominin subsistence behavior. Over the last several decades, however, BSM identification has remained contentious. Most investigations have relied on morphology to identify butchery marks and their patterning. Recently, 3D datasets have opened promising new avenues for investigation. However, analyses of these datasets have not yet taken advantage of the full 3D surface morphology of BSM.

In this study, the researchers demonstrate that 3D geometric morphometrics or G-M (GM), under the “Procrustes paradigm.” They coupled this with a Bayesian approach, probabilistically discriminating between marks caused by different butchery behaviors. This approach then provides a complete set of 3D morphological measurements and descriptions.

The researchers found that the new protocol resulted in satisfactory cleaned models of the original scans. However, it is important to note that subjective variation could have been introduced during the mark selection and isolation steps. If subjective error was added, it was likely introduced to all specimens in a random manner. Consequently, such errors are unlikely to have affected the differences between groups.

The new protocol and statistical methodologies presented in this study enable the nuanced examination of mark variability within the same mark class. This then explicitly links it to butcher action. This knowledge serves to connect observable variables, such as shape, to concrete physical parameters, such as the angle at which the stone tool was held. Also, it deepens the understanding of prehistoric butchery actions. It also has the potential to transform the way researchers conceptualize and classify variations in cut mark morphology. Overall, the results of such investigations have the potential to significantly alter interpretations of early hominin ecology and behavior.