As with other stone tools, bifaces can give evidence for the behavioral and technological strategies pursued by prehistoric people on the basis of task, as well as varying levels of ability. Do certain tool forms appear more commonly during some time periods over others? Can patterns in biface production be recognized, patterns that may reflect knapper ability? If so, do these patterns change over time? Can degree of knapping expertise be recognized? These are the questions that biface analyses aimed to answer.
Variations on a Theme: Blanks and Preforms
More than 1000 bifaces and biface fragments were recovered from Zatopec. Most of these artifacts were identified as "blanks" or "preforms." If you consider the production of a stone tool as a linear series of events or stages--for example, beginning with thinning, proceed to shaping, and so on--each artifact represents a point along the path to stone tool production (or reduction, since the stone gets smaller as more of it is flaked to create the final shape). This is how archaeologists approached the task of identifying patterns and differentiating skill levels. Four reduction stages were identified: 1) early stage bifaces, 2) intermediate stage bifaces, 3) late-intermediate stage bifaces, and 4) late stage preforms. Additionally, criteria such as regularity of form, flaking pattern, frequency of errors, outline symmetry, and overall width of the biface relative to thickness were used to evaluate the approximate aptitude of the knapper(s). The figures below illustrate stages in the reduction sequence of Skill Level 4 bifaces (upper) and variability among skill level for Late Stage Preforms.
These analyses showed (not surprisingly) that length, width, thickness, and weight all decreased from Early Stage to Late Stage Preform. Flake scars, or the relics of flake removal, were increasingly diffuse and less pronounced throughout the reduction sequence, thus indicating that knapping most likely began with a hard hammer (e.g., quartzite cobble, etc.) and ended with a soft hammer (like an antler). Assessments of skill variation across reduction sequence showed that Late Stage Preforms exhibited the highest average skill. Additionally, analysis of skill level also indicated that Intermediate and Late Intermediate Stages are not as distinctly different as Early Stage and Late Stage Preform. Maybe future analyses should combine Intermediate and Late Intermediate Stages.
Formal Bifaces: Identifiable Types
In addition to "blanks" and "preforms," there were many formal types of bifaces identified in the lithic assemblage from Zatopec. Identified types present at Zatopec include Hare, Pipe Creek, Corner Tang, Granbury, Covington, and San Gabriel bifaces. Similar to projectile points, these biface types suggest a certain amount of temporal and geographic information about the people that once made, used, and left them behind. Archaeologists have recognized these particular forms as occurring at a number of sites in Central Texas. Examples of types identified at Zatopec are pictured below.