3D 360° surface morphometric analysis of pounding stone tools used by Hadza foragers of Tanzania: A new methodological approach for studying percussive stone artefacts

Abstract

Surface morphometry comprises a relevant set of techniques that provide objective tools to identify, map, and understand use wear patterns in stone tools. Thus far, these techniques have been applied mainly to 2D or 2.5D data, but their application to 3D 360º data is promising and still underdeveloped. Here, we apply new 3D techniques to calculate morphometric variables and to analyse surficial features and changes in pounding stone tools used for baobab processing among Hadza foragers of Tanzania. Baobab pounding stones were collected after use by Hadza foragers for processing the plant food and then 3D point clouds were acquired from laser scanners and SfM photogrammetry. Morphometry was conducted directly on 3D point clouds to avoid time-consuming and surface modifications related to more complex 3D data, such as meshing. Several morphometric variables were computed for the complete pieces (360º sphere) providing fast and accurate data to identify the detailed morphometric features of the artefacts. Additionally, stone surface changes due to baobab processing were measured by comparing the stone surface before and after use, thus enabling calculation of spatial abrasion patterns. Data were interpreted using multivariate exploratory statistical analysis. Differences in the effect of processing on surface morphology are likely explained by variations in raw source material and use. Results suggest that the traces produced by baobab processing on stone tools should be detectable in the archaeological record.

The application of 3D modeling and spatial analysis in the study of groundstones used in wild plants processing

“…By treating 3D surface measurements obtained through the use of a confocal microscope and processed with GIS software, the authors were able to identify and monitor significant changes in surface topography at a micro scale. The results suggested differences in the degree of modification occurring between active and passive elements used to break bone, with the anvils exhibiting deeper modification while larger surface areas were modified on the hammerstones (Benito-Calvo et al 2017) More recently, Benito-Calvo and colleagues (Benito-Calvo et al 2018) evaluated the high potential of the application of 3D 360°morphometric analysis in the analysis of pounding tools. Through the direct processing of 3D point clouds, the authors analyzed various morphometric variables on a complete tool, measuring patterns of modification related to the use of stone tools in baobab fruit processing (Adansonia digitate) processing by Hazda foragers in Tanzania (Benito-Calvo et al 2018).…”

“…The results suggested differences in the degree of modification occurring between active and passive elements used to break bone, with the anvils exhibiting deeper modification while larger surface areas were modified on the hammerstones (Benito-Calvo et al 2017) More recently, Benito-Calvo and colleagues (Benito-Calvo et al 2018) evaluated the high potential of the application of 3D 360°morphometric analysis in the analysis of pounding tools. Through the direct processing of 3D point clouds, the authors analyzed various morphometric variables on a complete tool, measuring patterns of modification related to the use of stone tools in baobab fruit processing (Adansonia digitate) processing by Hazda foragers in Tanzania (Benito-Calvo et al 2018). All of the aforementioned studies demonstrated how the application of quantitative approaches (e.g., GIS) in the analysis of stone tool use allows the identification of battered areas and the kinetics involved in the use of pounding tools.…”

The Internal, External and Extended Microbiomes of Hominins

“…Pounding tools, such as those employed by chimpanzees, would have made roots and tubers also easier to digest (Crittenden, 2016). Similar tools are used by many small-scale societies around the world, including contemporary subsistence foragers (Benito-Calvo et al, 2018) as well as by chimpanzees (and hence likely our LCA; Figure 2). All of this is to say that as our ancestors invented more kitchen implements they would have been able to pre-digest and pre-process some of their foods, allowing them to rely less on microbes in their guts to break down recalcitrant components of their diets, such as cellulose.…”

Functional analysis of sandstone ground stone tools: arguments for a qualitative and quantitative synergetic approach

“…In particular, a low degree of accuracy in blind tests has been pointed (see 2,3 ) together with the need to implement quantitative approaches to obtain more accurate use wear datasets and guarantee the comparability and reproducibility of functional results 3,4 . In this regard, several works have discussed the application of quantitative methods focused on surface measurements to knapped and ground stone tools (henceforth GSTs), at both macro and microscale [5][6][7][8][9][10][11][12][13][14] . A variety of equipment and techniques has been tested, including confocal microscopy 5,6,9,15 , atomic force microscopy 16 , surface textural imaging 17 , laser profilometry 9,18 and 3D modelling [11][12][13]14,19,20 .…”

“…However, despite the long history of research on prehistoric GSTs, we believe there are important issues that still need to be addressed in order to advance the reliability of functional interpretations concerning this technology: (a) the demand for a shared analytical workflow for the functional analysis of both experimental and archaeological GST assemblages; (b) open DANTE Diet and Ancient Technology Laboratory, Department of Oral and Maxillo Facial Sciences, Sapienza University of Rome, Via Caserta 6, 00161 Rome, Italy. * email: emanuela.cristiani@uniroma1.it the lack of an exhaustive quantitative dataset concerning surface modifications associated with different uses; (c) to what degree residues hinder the development and appearance of use wear through optical microscopy; (d) the need to consider GSTs in their entire dimensionality 11 ; and (e) the role of the researcher subjectivity in the functional interpretation.…”