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Morphology of Lithic Artifacts: Experimental and Morphometric Approaches

Periodic Reporting for period 2 - MORPHOLITHEX (Morphology of Lithic Artifacts: Experimental and Morphometric Approaches)

Période du rapport: 2019-10-01 au 2020-09-30

MORPHOLITHEX project set out to better understand how prehistoric people made stone tools. Archaeologists have learned, over several decades of replicative experimental work, that flintknapping is a rather complex motor skill. They understood that the person producing a stone tool can control its final form by manipulating the various aspects of tool production: shaping the geometry of the core, the angle of the platform edge, how deep into the platform a core is struck, the angle of the blow, using hammers of different size and shape. Archeologists have used replicative experiments to show how each of these variables affects the outcome of the flake. Moreover, it was stressed by the researchers that how the knapper controls all these aspects, testifies to the predetermination of a blank form and is thought to capture the cognitive and learning abilities of knappers. However, the flintknapping process is so internalized that, for the knapper, it is very difficult to evaluate objectively the exact effect each of these variables have, separately and especially how they interact with one other.

MORPHOLITHEX aimed to parse out the main components of the knapping processes that have a crucial impact on the final stone tool product. It used artifacts produced in a simulated knapping setting (a custom-built machine) that makes it possible to control several variables relevant for flintknapping and thus evaluate their importance – independently and in interaction with other variables - in the final size and the shape on an artifact. Cores made out of glass are knapped in a machine that uses pneumatic cylinder or hydraulic press to remove flakes, thus imitating flintknapping. In this setting, it is possible to control many, if not all the variables that are under control of the knapper: core shape, platform angle and depth, angle of blow, hammer type.

Flakes coming off the cores in this experiment were 3D scanned and advanced methods are used to analyze the data: 1) 3D geometric morphometrics to better capture size and shape, 2) advanced statistical modeling to investigate the simultaneous effects of different variables, and especially their interaction.

This work contributed to our understanding of how stones break. It addressed the underlying rules of flake formation, that will further help archaeologist better understand how prehistoric people exploited these rules in the course of Prehistory.
The first experiment conducted in this project examined if the glass is the appropriate material to use in experiments involving knapping. Most controlled experiments conducted thus far used glass cores. Here we used different raw materials that knappers in prehistory used (basalt, obsidian, flint), to see if the results obtained with glass can be replicated. The results of the experiments showed that the raw materials knap in the same way as glass, confirming the validity of previous experiments and further supporting the continuation of the use of glass as a main material in experiments in lithic technology.

Several experiments were conducted in the Laboratory for the Study of Ancient Technology at the University of Pennsylvania in Philadelphia over almost 20 years, that examined various variables affecting the resulting flakes (core morphology, platform depth and angle, angle of blow, platform beveling). Dataset of glass artifacts stemming from these experiments are foundational to understanding how flakes are formed. Metric and attribute data collected on the experimental collection provided a basis for several collaborative studies that are published/in press/in preparation that make a significant contribution to the questions of stone artifact formation. One published article reports on an identified platform surface angle which directly follows from the Hertzian cone constant angle and is an important determinant in flake size and shape. An article in press is presenting a study that analyses the role of platform width in flake size and shape. Under preparation is a preparing a publication that summarizes the results of experiments conducted in the Lab at the University of Pennsylvania.

The experimental artifacts have also been scanned and their 3D model generated. The 3D data collected on the entire collection from Dibble experiments, enabled a formulation of a geometric model of stone fracture that explains flake size and shape relative to parameters of exterior platform angle, core morphology, angle of blow, etc. Based on this dataset, this project aimed at developing a model of the initiation and propagation phase of flake formation. The publication is currently under preparation.

In sum, the results of these analyses are detailed in 5 papers in open-access peer-reviewed journals (published, in press, in preparation) and also presented at international conferences and invited talks. The researcher has created and maintained a webpage for the project (https://morpholithex.wordpress.com).
The study of lithic artifacts from the controlled experiments made several important contributions to our understanding of how stone tools are made. One significant contribution to the field of experimental archaeology was made by showing that the raw materials used in the past flake in the same way as glass. This validates the results of the experiments in archaeology that have been conducted in the past and supports the use of glass as a material in experimental knapping.

Further, instead of using standard methodology of attribute analyses and replicative experiments, this project turned to controlled experimentation and statistical modeling to tackle the questions of fracture mechanics and build explanatory models of flake formation. By better understanding of the principles of stone fracture mechanics, the results of this project improve our knowledge about how people in the past understood and used those rules to produce stone artifacts. Because they relate to the underlying mechanisms – physical laws and models - these results are applicable to chipped stone technologies from various periods in Prehistory.

The collaborative nature of this project and the stimulation of the archeological research based on controlled experiments has increased the competitiveness of the ERA in this field.

Publications are and will be made available in ‘gold’ or ‘green’ open access. The metric and attribute data and 3D models of the experimental artifact collections produced at the Department of Anthropology at the University of Pennsylvania in Philadelphia will be made available, together with the code used to produce results, once the articles are published. This dataset will be an excellent resource for researchers worldwide interested in addressing various research questions related to the stone tool production in any period of Prehistory. Both attribute and 3D datasets will also be a valuable resource for teaching stone tool technology, in high-school or University-level classes, particularly in online teaching settings.
Simulated knapping with Instron hydraulic press
Placing landmark points on a 3d model of a flake
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