Influence of force and duration on stone tool wear: results from experiments with a force-controlled robot

Abstract

Many studies have shown that micro-wear analysis can identify some parameters such as worked material and motion direction with varying degrees of success. However, because experiments have traditionally been carried out by un-monitored humans, we do not fully understand the role of force in wear formation. Here we compare the amount of wear produced by duration vs. applied force in a controlled experiment and using both the inspection of optical images and quantitative parameters describing surface topography. We used flint flakes attached to a force/ torque controllable robot arm to scrape standardized beech wooden planks under constant force profiles. The force profiles were obtained by previous experiments in scraping described in Pfleging et al. (2015). We varied the force level and use duration among the experiments. Worn pieces were imaged with an Alicona InfiniteFocus G4 microscope and the polished parts of the flakes were analysed using areal field parameters from metrology. The data is publicly available on the internet. Results indicate that use duration contributes more significantly to polish formation than force, confirming assumptions made in human experiments performed in the 1980s. Moreover, simple metrological height parameters appear inadequate for capturing the degree of polish. We conclude that more sophisticated quantitative methods are required to go beyond the subjective human evaluation of optical images to reconstruct past human action.

A versatile mechanized setup for controlled experiments in archeology

“…Collaborative robots (Pfleging, Iovita, and Buchli 2019;Schmidt et al 2019) have a varying number of articulations to produce a wide range of movements at the tool end, i.e. where the sample is attached.…”

“…Bebber and Eren 2018). Consequently, controlled experiments have been conducted with variable degrees of control (Lin, Rezek, and Dibble 2018) depending on the study's research questions (compare for example Pedergnana and Ollé 2017;Pfleging, Iovita, and Buchli 2019). If some factorswhether known but ignored, or unknownare not controlled, they become confounding factors and will potentially blur the signal with noise (Lin, Rezek, and Dibble 2018;Marreiros et al accepted).…”

“…Dibble and Pelcin 1995;Dibble and Rezek 2009;Dibble and Whittaker 1981;Dogandžić et al 2020;Mraz et al 2019), formation of use-wear (e.g. Astruc, Vargiolu, and Zahouani 2003;Martisius et al 2018;Pfleging, Iovita, and Buchli 2019;Vargiolu, Zahouani, and Anderson 2003), projectile technology (e.g. Bebber and Eren 2018;Cohen et al 2016;Iovita et al 2014;Loendorf et al 2018;Schoville et al 2017;Schoville and Brown 2010;Shea, Davis, and Brown 2001;Waguespack et al 2009;Wilkins, Schoville, and Brown 2014), tool performance (e.g.…”

“…Poulis 2016, 2017). While these setups were appropriate for the questions addressed in the publications, they lacked either sensors to monitor and/or control parameters during the experiments (Collins 2008), very precise movements (Pfleging, Iovita, and Buchli 2019;Schmidt et al 2019; see section 2 below), or general versatility (e.g. Dibble and Rezek 2009;Iovita et al 2014;Martisius et al 2018), which eventually limit the applicability of the setups to other actions and questions.…”

Controlled experiments in lithic technology and function

“…One of the most discussed topics in this issue is the use of controlled experimental replication to identify and interpret the impact of raw material variation on past human technological decision-making. These papers explore the manipulation of the raw material (Mackay et al 2018), lithic tool production and design (Dogandžić et al 2020;Pargeter et al 2018), tool efficiency and durability (Abrunhosa et al 2019 and Pereira et al submitted), and tool use (Pfleging et al 2018).…”