Date Published: March 21, 2017
Publisher: Public Library of Science
Author(s): Michael J. Shott, Nuno Bicho.
North American lithic analysis often assigns biface preforms to discrete, successive stages defined in Callahan’s influential study. Yet recent research questions the stage concept, emphasizing instead a continuous view of the reduction process. To compare stage and continuum approaches, their assumptions are tested in experimental replicas, including Callahan’s, and empirical Paleoindian preform assemblages. In these samples, biface reduction is a process that can be tracked and measured by continuous measures of size and reduction allometry. The process is characterized by continuous variation in the rate at which preform weight declines with preform volume. That is, weight declines at an ever-declining rate through the production process. Reduction is complex, but understood better as an allometric process than as a sequence of technological stages. “Stage” may be a useful heuristic or summary device, but preform assemblages should be analyzed in detail to reveal the continuous allometric processes that govern biface production.
All archaeologists know that bifaces are chipped stone tools worked on two opposing faces separated by retouched edges. The category “biface” includes finished tools—points of various defined types and/or other functional classes like knives—but also unfinished specimens that span a range of reduction from slightly modified flake blanks to nearly finished tools. This paper concerns the process of biface reduction. It evaluates two views of the process’s nature, as continuous or as segmented into real, technically determined, stages .
Continuous measures z-weight and JTI patterned with overall preform size as given by z-PC1. At successive Callahan “stages,” most regression slopes against z-PC1 declined. That much is consistent. However, individual datasets did not scale similarly because the same Callahan “stages” sometimes yielded significantly different z-weight slope coefficients. That much is ambiguous. In particular, Callahan’s own dataset differed significantly in z-weight slope coefficient from most others, which in turn scaled nearer to one another.
None of this is to criticize biface-production stage approaches generally, nor to suggest that reduction is continuous in all salient respects. Callahan’s (, Table 10) model includes categorical variables that may pattern with assigned stage. Unfortunately, some are difficult to replicate or of unknown relevance (e.g., regularity of outline, “degree of concentration during fabrication,” “degree of trim,” “nature of reduction emphasis” which in Hill’s [, Table 1; see also , Table 5–23] approach signify relative emphasis upon edge, thinning, and outline, however determined).