THE OBSIDIAN BLADE SEQUENCE AT EL UJUXTE, A LATE PRECLASSIC SITE ON THE SOUTH COAST OF GUATEMALA

Systematic data on about 1,200 blades from this site were summarized in terms of three ceramic phases (defined by Love 2002b) for the same site. That is, we assigned blades to phases based on the ceramic content of each provenience. Regular phase-by-phase decreases occurred in blade dimensions, weights, and length-to-width ratios. We predicted these results based on earlier findings from the site of La Blanca (Nance and Kirk 1991). The trend appears also within the latest Pitahaya phase, even at the level of the excavation unit. Blade densities decrease through Pitahaya deposits, as well, and the blade sequence is discussed in terms of an increased scarcity of obsidian or obsidian blades traded to the region. In earlier research at the Middle Preclassic site of La Blanca on Guatemala’s southern coast and now at the nearby Middle to Late Preclassic site of El Ujuxte (Figure 1), we have documented a gradual decrease in prismatic blade size through time. Much of the real cost of blades to these people would have been in transporting blade-quality obsidian from the Guatemalan Highlands (see Tabares et al. 2005 on El Ujuxte obsidian sources). Gradually learning to cope with smaller blade-tool bits might have lowered the cost per blade to El Ujuxte importers. Human porters could have transported more small blades per load, more small cores versus larger ones, and so on. So, one possible explanation for the decrease in blade size at these sites is increased efficiency on the part of consumers. If, however, smaller blade size was dictated by suppliers in either the highlands or elsewhere on the southern coast and not recipients at El Ujuxte, then we might be looking at the problem of interrupted trade and obsidian-blade scarcity. While there are many difficulties surrounding the study of blades, the technique used here was to create a computerized dataset, a matrix in which each data line contained information about an individual blade, and each column contained information about a variable describing the blades or their provenience in the site. Variables systematically recorded have to do with blade morphology, aspects of edge wear, edge alteration, and blade size. For the purposes of this research, the term blade refers to either a complete prismatic blade or a blade section created when a blade is snapped across its longitudinal axis. Blade fragments without complete cross-sections were excluded from the dataset. It is important to state at the outset that this is not a study of the technology of blade production. The authors never examined all of the obsidian from El Ujuxte but were sent about 3,700 catalogued specimens of blades and possible blades chosen by laboratory personnel. From these, we selected 1,260 blades according to criteria stated earlier. In earlier research, C. Roger Nance and Katharine Kirk (1991) proposed a sequence of changing obsidian-blade complexes for the Middle Preclassic site of La Blanca on the southern coast of Guatemala. That study was based on samples of blades from four different portions of the site ceramic sequence. Michael Love (2002a) excavated La Blanca and also defined the ceramic sequence there. We found that through time, obsidian blades from La Blanca gradually decreased in size in terms of decreasing lengths, widths, and thicknesses, as well as weights. Blade proportions changed, with length-to-width ratios becoming progressively smaller. Edge wear increased on the lateral edges of blades through the sequence, and resharpening of blades became more common, as shown by increased bipolar modification, which served to renew lateral blade edges. All of this suggested an increasing scarcity of obsidian for the inhabitants of La Blanca. As for La Blanca, the El Ujuxte obsidian study followed that for ceramics, and ceramic-phase designations were used to determine relative chronological positions for obsidian samples (collected by excavation unit and 10 cm level). Also consistent with the La Blanca research, all pieces of obsidian were collected systematically by screening deposits through one-eighth-inch hardware cloth. Love also excavated El Ujuxte and recently described the site ceramic sequence, dividing it into three phases. They fall into the