Stage and continuum approaches in prehistoric biface production: A North American perspective

Michael J Shott,Nuno Bicho

doi:10.1371/journal.pone.0170947

Abstract

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.

Highlights

All archaeologists know that bifaces are chipped stone tools worked on two opposing faces separated by retouched edges
Callahan and other datasets to which it is compared below scale somewhat differently in the range of original variables, which complicates direct comparison of their regression results
To minimize scale differences that can affect principal-components analysis (PCA), data were transformed to standard scores (“z-scores”) for each dataset separately from others. z-scores rescale raw data to units of each variable’s standard deviation, their sign indicating that they are above or below the mean

Summary

Introduction

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—and 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 [1]. A blank is any piece of stone that can be reduced to a tool such that “The shape or form of the final product is not disclosed in the blank” ([3], 42) except in the broadest sense. A preform “is an unfinished, unused form of the proposed artifact. It is larger than, and without the refinement of, the completed

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