Human Trampling

The first Special Issue of Intersecciones en Antropología, Taphonomic Approaches to the Archaeological Record, gathers papers that apply a taphonomic approach to the study of several types of archaeological remains in order to discuss the potential of expanding the scope of this theoretical and methodological perspective in Archaeology. As a whole, this collection of papers provides an overview of current investigations in Argentina engaged with methods that deal with formation processes and their specific effects on the different components of the archaeological record to answer broad archaeological questions.

This paper presents the results of a trampling experiment on obsidian artifacts conducted as part of a larger archaeological program aimed at assessing the effects of postdepositional processes on lithic artifacts. Flaked artifacts were made from obsidian nodules from Huenul source (Neuquén, Argentina) and were laid on two plots-hard and soft substrate. Here we report the breakage frequency and artifact metric variables relevant for fracture occurrence. Following the methodological proposal to assess the Trampling Fragmentation Potential (TFP), we apply the data mining technique known as decision tree to analyze the experimental obsidian datasets. Results show that fracture ratio is significantly higher on hard substrates, and that the value of maximum fracture thickness shows no variations in obsidian. Finally, including the obsidian dataset to the decision tree showed that certain raw materials may modify the relevant variables and/or their influence on the TFP.

RESUMEN
Como continuación de un proyecto destinado a contribuir al conocimiento arqueológico de los efectos de los procesos post-depositacionales sobre los materiales líticos, se realizó una experiencia de pisoteo sobre artefactos de obsidiana. El experimento incluyó el planteo de dos pistas-una sobre sustrato blando y otra sobre sustrato duro-en las que se depositaron artefactos experimentales manufacturados a partir de nódulos de obsidiana procedente de la fuente Huenul (Neuquén, Argentina). Siguiendo la propuesta planteada para evaluar el Potencial para la Fragmentación por Pisoteo (PFP), los datos experimentales son analizados con la técnica de data mining denominada árbol de decisión. Se informan las frecuencias de fractura y las variables métricas artefactuales relevantes en su ocurrencia. Como fuera registrado en experimentaciones previas, se observó que el sustrato duro promueve la ocurrencia de fracturas y contrastamos los espesores máximos de fracturas obtenidos. La incorporación de los datos de obsidiana al árbol de decisión mostró que ciertas materias primas pueden modificar las variables de relevancia y/o su influencia sobre el PFP.

Palabras clave: experimentación; obsidiana; potencial para la fragmentación por pisoteo; tafonomía lítica.

The current paper reports an experimental case study to test the heterogeneity of faunal assemblages from the Early-Middle Pleistocene Layers V-5 and V-6 of the Gesher Benot Ya’aqov Acheulian site (Israel).
Tumbling and trampling experiments were initiated to gain qualitative insight into processes of bone modification and to assess the timing of the biostratonomic chronology, as it was assumed that both mechanisms were responsible for the formation of striations documented on the bone surfaces from the
site. The tumbling experiments mimicked sediment movement in a calm lacustrine shoreline environment whereas the trampling experiments investigate the role of animal/hominin activities in dry, muddy and wet environments. Models for the internal operational sequence of an abrasional process due to uniand
multidirectional water movement and of a trampling scenario are presented. These models are used for the interpretation of the fauna from Gesher Benot Ya’aqov.

Macrofracture analysis is an experimentally derived method used as an initial step in investigating the hunting function of stone artefacts. Diagnostic impact fractures, which can only develop as a result of longitudinal impact, underpin this method. Macrofracture analysis recently gained favour in Middle Stone Age studies, supporting hypotheses for effective hunting during the late Pleistocene in southern Africa. However, the factors affecting diagnostic impact fracture formation and the interpretation of these fracture frequencies are not yet fully understood. This paper outlines a set of experiments designed to test macrofracture formation under human and cattle trampling and knapping conditions. The results show that: (a) macrofractures occur frequently when stone artefacts are trampled by cattle and humans and in knapping debris; (b) diagnostic impact fractures occur on some of the trampled flakes and knapping debris (3%), but significantly less often than in previous hunting experiments; (c) when they do occur, they are likely produced by longitudinal forces similar to those experienced during hunting; (d) considering artefact morphology is important during macrofracture analysis; and (e) macrofracture analysis is not a standalone method, but is most useful as part of a multi-analytical approach to functional analysis. These experiments help to establish a significant baseline diagnostic impact fracture frequency for the interpretation of archaeological macrofracture frequencies.