Updated: May 19, 2019
Robert Z. Selden, Jr. (1,2) and John E. Dockall (3)
(1) Heritage Research Center, Stephen F. Austin State University (US) (2) Cultural Heritage Department, Jean Monnet University (FR) (3) Prewitt and Associates, Inc. (US)
This post is a brief overview of a forthcoming article. Links to access the preprint of that article, as well as the preprint, article, and poster from the Gahagan biface morphology project that immediately preceded this one can be found at the end of this post in the Further Readings section.
This investigation follows a recent morphological study of the three largest samples of Gahagan bifaces, where a significant difference in biface shape was found to occur between Gahagan bifaces from the Mounds Plantation site (16CD12) and those recovered at the Gahagan Mound (16RR1) and George C. Davis sites (41CE19). This endeavor seeks to further characterize local morphological variation using 64 intact or reconstructed Gahagan bifaces from contexts where two or more specimens were recovered at the Gahagan Mound, George C. Davis, and Mounds Plantation sites. Gahagan bifaces are currently thought to be products of trade between east Texas Caddo groups and central Texas hunter-gatherers. The bifaces were scanned and analyzed using the tools of geometric morphometrics to identify whether Gahagan biface morphology differs between and among Caddo features. The results of this study provide a preview of the dynamic morphological relationships associated with Gahagan bifaces recovered from Caddo archaeological features. A preliminary sequence of geographic shape change is postulated for Gahagan bifaces that potentially indicates modifications employed by Caddo knappers, and not those of the hunter-gatherer groups thought to have manufactured them.
The Gahagan type was suggested by Clarence H. Webb at the Caddo Conference in 1970, and was intended as a replacement for what Newell and Krieger had previously called Copena knives based upon similarities in form, but not technology, between specimens found at the George C. Davis site (Figure 1) and those reported by Webb and DeJarnette in Alabama. Gahagan bifaces are currently thought to differ from Copena bifaces in morphology and technology, and were named for the finely-crafted bifaces found by Moore at Gahagan Mound. Shafer later advanced a useful technological and morphological description for the type. Like the Gahagan bifaces from the George C. Davis site, those from the Gahagan Mound and Mounds Plantation sites (Figure 1) demonstrate a relatively high degree of intra-type morphological variation.
This analysis of Gahagan biface morphology serves as an extension of previous contextual comparisons conducted by Shafer at George C. Davis, and enlisted the intact or reconstructed samples from George C. Davis, as well as those from the Gahagan Mound and Mounds Plantation sites. Through a comparison of biface morphologies by feature, additional insights were achieved that expand upon the previously-identified difference in morphology found to occur in the assemblage from Mounds Plantation. This study demonstrates that while the sample of Gahagan bifaces from Burial Pit 2 at Mounds Plantation is morphologically distinct from those recovered in features at the Gahagan Mound and George C. Davis sites, bifaces from Burial Pit 5 at Mounds Plantation do not differ significantly from Burial Pits 2 and 3 at Gahagan Mound (Figure 2). Additionally, the size of those bifaces recovered from Burial Pit 3 at Gahagan Mound were found to display greater size variation among individual bifaces relative to those from Burial Pit 2 at Mounds Plantation. Morphological integration was also significant, indicating that Gahagan biface blade and base morphologies are correlated. These results illustrate the dynamic range of morphology that occurs across Caddo features using the three largest samples of Gahagan bifaces found at Caddo sites.
The results of this study have aided in the identification of morphological differences among Gahagan bifaces recovered from different contexts (Figure 3); however, these results also point to similarities among the various contexts and assemblages. One such similarity occurs between the Gahagan Mound and George C. Davis assemblages, confirming the supposition by Shafer that the two assemblages compare favorably. It is also interesting that the Gahagan bifaces in Burial 5 at Mounds Plantation do not differ significantly from either context at the Gahagan Mound site, that they do differ significantly from all contexts at George C. Davis, and it is the only context that does not differ significantly from Burial 2 at Mounds Plantation.
The bulk of Gahagan bifaces in these three assemblages are currently thought to have been imported from central Texas, and—if true—the spatial location of recovery would complement the results of the morphological analysis, lending support to an incremental sequence of shape change where Gahagan biface shape might be said to differ in relation to distance of recovery from the (unconfirmed) raw material sources in central Texas. Further work is warranted to clarify the diversity of raw materials used in the production of Gahagan bifaces, which could have far-reaching implications. While previous results indicated that the differences in Gahagan biface morphology might be attributable to two (north/south) communities of practice, these results support an interpretation that is more dynamic.
While morphological similarities in Gahagan biface shapes recovered from contexts at George C. Davis and Gahagan Mound, and Gahagan Mound and Burial Pit 5 at Mounds Plantation might be interpreted to correspond with a hypothetical measure of distance from the raw material source, the morphological similarities found to occur between Burial Pits 2 and 5 at Mounds Plantation are not. Further tests are warranted, to include comparisons of Gahagan biface shapes that articulate with a specific burial (i.e., discarded near a forearm or femur) and those deposited as a group outside of a specific burial (i.e., discarded along the northwest margin of burial pits).
There are substantive challenges associated with the interpretation of Gahagan biface morphology. Shafer notes that the makers of Gahagan bifaces likely resided at or near a location with ample raw materials. The working theory that Gahagan bifaces were not a product of Caddo manufacture is further evidenced by the absence of production failures at Caddo sites, and the absence of similar, locally-sourced raw materials. In a comparison of lithic reduction strategies, Shafer compared the debitage sample from the western excavations at the George C. Davis site with that of 41MQ4, an Archaic (preceramic) site located around 100 km south of the Davis site, where raw material quality likely posed similar limitations on makers. Results indicated that the reduction strategy employed by the Caddo at George C. Davis was distinct from that of the Archaic sample. That the Caddo are thought to have employed a distinct lithic reduction strategy is key to the interpretation of Caddo stone tools, which may be further evidenced by the retouch or refurbishment of Gahagan bifaces. However, discriminating between flake scars produced by central Texas knappers and those made later by the Caddo is a substantive challenge that has not yet been addressed.
Recent studies have enlisted geometric morphometrics to analyze flake scars and bifacial asymmetry in an effort to better characterize reduction techniques, social interaction, and cultural transmission. Gingerich and colleagues demonstrated that geometric morphometric methods were able to better differentiate between techniques employed by individual knappers when compared to traditional orthogonal measures. Gingerich and colleagues also suggest that factors of manufacture (i.e., technology, technique, and individual knapping style) can be gainfully discriminated using 3D model-based flake scar contours. Those data needed to conduct a similar study associated with Gahagan biface flake scars were collected for this study of morphological variability among Caddo features. The pursuit of a flake scar analysis for Gahagan bifaces would warrant only minor modifications to the current methodological approach. The addition of flake scar analyses would expand the range of research questions that could be asked of these data to include those associated with whether the Caddo that inhabited these three important mound sites were importing Gahagan bifaces from the same, or different, producers in central Texas based upon evidence of knapping technique and style.
Through the use of morphological attributes associated with Gahagan biface blade and base shapes, similarities and differences were identified among archaeological contexts at three mound centers in the southern Caddo area. Blade and base shapes were found to be morphologically integrated, and the size of those bifaces recovered from Burial Pit 3 at Gahagan Mound were found to display greater size variation among individual bifaces relative to those from Burial Pit 2 at the Mounds Plantation site. Those patterns identified in this study may articulate with a similar shift in Caddo bottle shape across the same geography. Coupled with data from the geometric morphometric analysis of flake scars, physical analyses of debitage from central Texas sites and additional Caddo sites would have utility for comparative endeavors. This should include clarification of the material culture signatures—preform flakes, punch flakes, biface thinning flakes, etc.—associated with Gahagan biface manufacture. Biface thinning flakes produced from thin, flat bifaces will not only exhibit a low curvature profile, but should begin to expand laterally toward the distal end, as the flatter surface allows the flake shape to expand, rather than being guided by the surface curvature of the biface. Flake shape and debitage analyses should occur congruently where feasible. Further work is warranted to better characterize the variable morphology of Gahagan bifaces within and beyond the southern Caddo area. Tests that identify potential locations of manufacture would be of great utility, as would those that posit differential sequences of production and the characterization of retouch strategies employed by Caddo knappers, and still others that test whether—and if so, to what extent—these patterns are discernible in the many fractured and incomplete specimens previously assigned to the type.
We extend our gratitude to the Caddo Nation of Oklahoma, the Williamson Museum at Northwestern State University, the Louisiana State Exhibit Museum, and the Texas Archeological Research Laboratory at The University of Texas at Austin for the requisite permissions and access needed to generate the 3D scans of the Gahagan bifaces. Thanks to Harry J. Shafer, Jeffrey R. Girard, Hiram F. (Pete) Gregory, and Timothy K. Perttula for their pre-submission reviews of this manuscript. Thanks also to Dean C. Adams, Emma Sherratt, and Kersten Bergstrom for their constructive criticisms, comments, and suggestions throughout the development of this research design, and to the editors and anonymous reviewers for their comments and constructive criticisms that further improved the manuscript. Components of this analytical work flow were developed and funded by a Preservation Technology and Training grant (P14AP00138) to RZS from the National Center for Preservation Technology and Training, and funding to scan the Gahagan bifaces at the Williamson Museum at Northwestern State University, Louisiana State Exhibit Museum, and Texas Archeological Research Laboratory at The University of Texas at Austin was provided to RZS by the Heritage Research Center at Stephen F. Austin State University.
Preprint of 2019 article:
Selden Jr., Robert Z. and John E. Dockall. 2019. “A Comparison of Gahagan Biface Morphology across Caddo Features at the Gahagan Mound, George C. Davis, and Mounds Plantation Sites.” SocArXiv https://doi.org/10.31235/osf.io/fyw2d
2019 Conference poster:
Selden Jr., Robert Z., John E. Dockall, and Harry J. Shafer. 2019. "Lithic Morphological Organization: Gahagan Bifaces from Texas and Louisiana." Stephen F. Austin State University, accessed March 1, 2019. https://scholarworks.sfasu.edu/crhr/266/
2018 DAACH article and preprint:
Selden Jr., Robert Z., John E. Dockall, and Harry J. Shafer. 2018. "Lithic Morphological Organisation: Gahagan Bifaces from the Southern Caddo Area." Digital Applications in Archaeology and Cultural Heritage 10:e00080. https://doi.org/10.1016/j.daach.2018.e00080
Selden Jr., Robert Z., John E. Dockall, and Harry J. Shafer. 2018. "Lithic Morphological Organisation: Gahagan Bifaces from the Southern Caddo Area." SocArXiv https://doi.org/10.31235/osf.io/u7qfr