Scientific drawings, including maps, are increasingly recognized as theory-laden media for conveying information. The degree to which this quality impacts archaeological interpretations is revealed in the history of the published maps of La Venta, a Formative period Mesoamerican regional center. La Venta is pivotal to understanding the Olmec culture of Mexico’s Gulf Coast, yet archaeological knowledge is based primarily on one small portion of the site, Complex A, excavated in 1955. Since destroyed, Complex A is now known especially through visual representations. A review of the Complex A maps in the original field report and subsequent publications demonstrates how these technical drawings have sometimes superseded the textual excavation data in generating and disseminating archaeological knowledge. Over time the maps have become more schematic and misleading, impeding understandings of La Venta and its role in regional cultural manifestations. Reliance on totalizing plan maps has led most archaeologists to overlook the 1955 excavators’ major interpretations of the construction history of Complex A. However, the 1955 conclusions regarding the longevity of the formal design rules of the complex, reiterated by later archaeologists precisely because they are clearly visible in plan maps, are less well supported by the stratigraphic evidence.

The labor investment in ancient monumental architecture is an important factor in hypotheses concerning a society’s size, organization, and social complexity. Most methods of quantifying labor expenditures are limited to simply designed structures with a minimal number of elements. Due to the lack of practical analytical methods, complex architecture is often described subjectively, offering little quantitative value, resulting in inferences that could be misleading or wrong. Using Ciudadela Rivero at the site of Chan Chan, Peru, as a case study, this research employed construction industry-standard planning, estimating, and scheduling tools to calculate the labor requirements and construction times under various building scenarios. Additionally, the application of Critical Path Method scheduling provides the means to model and compare numerous building scenarios by simulating the effects of various construction and labor organization strategies in their cultural context. The results for Ciudadela Rivero revealed a labor input of over two million labor hours, which could be accomplished by a modest labor force of as few as 250 workers over a six-year period. These data affect numerous archaeological hypotheses concerning scale of construction, organization of labor, and complexity of social organization.

The archaeological setting of the La Tolita—Tumaco culture is briefly discussed as a framework for the examination of the metallurgy of the area, in particular the gold—platinum alloys used to make platinum-coated gold objects, platinum—gold sintered alloys, and platinum—gold foil—plated objects. The sophisticated approach to the manipulation of metallic materials resulted in several notable advances being made by the La Tolita—Tumaco culture: the production of extremely fine rectangular wire, bimetallic tumbaga alloys, small lead spheres inlaid with platinum, soldering, granulation, and a degree of sophistication to metalworking that is very impressive and, in some cases, unique in the world. Some selected examples are discussed, and the microstructure of a representative selection of the La Tolita material, bimetallic tumbaga construction, the initial sintered gold—platinum product, platinum-plated gold, and heavily worked gold—platinum composite artifacts are presented.

The Carboncillo area in the southern highlands of Ecuador is identified as the only confirmed source of archaeological obsidian located in the country outside of the northern highlands and is the first identified in the large gap between the known Ecuadorian and Peruvian sources. With the identification of this source, it can no longer be assumed that all obsidian found in Ecuador came from sources in the northern highlands. Thus the Carboncillo source has significant implications for interpreting patterns of long-distance exchange in the Andes, especially in southern Ecuador and the far north of Peru. A geochemical analysis of the Carboncillo material shows that it can be easily distinguished from the obsidian from other Ecuadorian sources. A provenance study of archaeological obsidian samples from the southern highlands of Ecuador using x-ray fluorescence demonstrates that the Carboncillo obsidian was used at the Preceramic site of Chobshi Cave and at a number of late prehispanic sites in the Saraguro region. The results indicate a high level of sociopolitical and economic isolation in late prehistory, most likely tied to a preoccupation with warfare between neighboring groups, and provide additional evidence that the economic organization of the southern highlands differed markedly from that of the north during this time.

Artifacts made from Quispisisa obsidian are widely disseminated in the Peruvian Andes, but the geological source of the Quispisisa geochemical type was only recently located in southern Ayacucho. Following the positive identification of the source in 1999 by Richard Burger and colleagues, we found evidence of broad quarrying activities in unexplored portions of the source area. We describe 34 quarry pits, some as large as 80 m across, together with evidence of early-stage lithic reduction at the source. We encountered high concentrations of reduction debris associated with more extensive knapping in two localities, but our preliminary evaluation of surface evidence suggests that much of the material quarried was removed from the area as intact nodules or after minimal reduction at the source area.