Stone tools from the inside out: radial point distribution

The concept of shape is central to the classification of material culture. In the case of lithic technology, archaeologists have attempted to characterize shape quantitatively and qualitatively using diverse methods ranging from manual caliper measurements and metric ratios to digital artifact scans and statistical analyses. Three-dimensional modeling has opened up new avenues for shape analysis that permit a more holistic perspective on how objects occupy space. As a result, researchers are able to explore new qualities of artifacts that were previously inaccessible through more traditional shape analyses. This paper outlines a new method for quantifying distribution of mass in lithic specimens from three-dimensional point-cloud data. Radial point distributions (RPDs) are calculated from point-filled models based on the distances of each point to the model centroid. The resulting distribution data provide a means of quantifying three-dimensional shape that is readily compared through statistical analyses. RPD calculation requires no manual specimen alignment or landmark identification, thereby removing major sources of subjectivity. It is argued that RPDs provide a means of quantifying the ‘balance’ of lithic specimens, such as handaxes, allowing researchers to explore this tactile aspect of stone tools in conjunction with more traditional visual aspects of shape.