|P1: Bipolar technique||
Analysis of the Calixtlahuaca stone tools has revealed that bipolar percussion was used to make stone tools in the city. So, what exactly is the bipolar technique (BP)? BP involves striking the top of a piece flakable stone placed on an anvil stone (see picture P1). As such, it enables the knapper to transmit force from both “poles” of a “focal” piece (Flenniken 1981). It is also effective for making implements out of small pieces of stone that are difficult to flake because the knapper is able to securely support them allowing for efficient flaking.
BP as a common technique for making stone tools is usually associated with the early Formative period (2000 B.C. to A.D. 250). By the late Formative, prismatic blade technology began to emerge, becoming the most important source of slicing, cutting and scraping tools in Mesoamerica in the centuries that followed (Clark 1981; Parry 1987). Hence, many people tend to think BP was largely absent in Mesoamerica after the Formative. So, the simple fact that the Calixtlahuacans were using it is somewhat of a surprise.
Of more than 6000 technologically diagnostic artifacts (those with features that indicate how they were produced), 11 percent were flaked with BP technology. This figure is not a majority, but it is significant. The BP artifacts we have identified include BP-flakes, “Scalar cores,” and bipolared blade sections. The BP-flakes (see picture P2) are variously shaped and have flake scars with ripples of force trending in opposite directions. Some were presumably flaked to make smaller tools - some were also used because they have use-wear on one or more edges.
|P2: Bipolar flakes|
because of the debate over their function (see picture P3). The term we use for this artifact is barrowed from Clark’s (1981) work in Formative period Chiapas. Artifacts similar to this one include the “scaled flake” (Parry 1987) and the piéce esquillées (Hayden 1980). One question is whether these three items were functionally different or had overlapping uses. They could have been used as 1) “bipolar cores” that yielded flakes, 2) and/or “chisels” or “wedges” used for some specific task, perhaps woodworking. My guess is that they had both functions.
|P3: Scalar core, front and
|P4: Bipolared blades -top
dorsal, bottom ventral view
|P6: Experimental blade
sections - top ventral,
Calixtlahuaca’s incorporation into the Aztec Empire meant more Pachuca green obsidian reached the city. Moreover, if prismatic blades were preferred and were more readily available in the Yata phase, then perhaps there was less pressure to recycle using bipolar technology. Ongoing research, including a chemical study of the gray obsidian artifacts will be evaluating these trends and what we think they indicate about life at Post-classic Calixtlahuaca.
Clark, John E.
1981 The Early Preclassic Obsidian Industry of Paso de al Amada, Chiapas, Mexico. Estudios de Cultura Maya 13:265-283.
De León, Jason
2008 The Lithic Industries of San Lorenzo-Tenochtitlán: An Economic and Technological Study of Olmec Obsidian, Penn State University.
Flenniken, J. Jeffrey
1981 Replicative Systems Analysis: A Model Applied to the Vein Quartz Artifacts from the Hoko River Site. Washington State University Laboratory of Anthropology. Submitted to Reports of Investigations. Copies available from 59.
1980 Confusion in the Bipolar World: Bashed Pebbles and Splintered Pieces. Lithic Technology 9(1):2-7.
1987 Chipped Stone Tools in Formative Period Oaxaca, Mexico: Their Procurement, Production, and Use. Memoirs of the Museum of Anthropology. University of Michigan, Ann Arbor.