Dorothy Hosler

Professor Emerita of Archaeology and Ancient Technology

Primary Impact, Materials, Research Type

Contact Info

Office: 8-211


Professor Dorothy Hosler’s research examines the extraction, processing and production of copper and copper-based alloys objects from northern South America and West Mexico and the relation of these two ancient technologies to each other. Initial work compared alloy-properties and design of metal objects from Andean South America with those from West Mexico (Michoacán, Guerrero, Jalisco, Nayarit, Colima). Results demonstrated that Andean fabrication techniques, alloy systems and some design types were introduced to West Mexico sometime after 700 CE. Indigenous artisans worked in this mineral-rich region, where local ideologies created a pronounced interest in the acoustical properties of copper, copper-silver, copper-tin and copper-arsenic alloy bells and other sounding instruments.

These people also displayed an intense interest in metallic color, particularly in shimmering golden and silvery hues, both in castings (silver-copper, copper-arsenic, copper-tin bells) and in silver-copper and high-tin bronze sheet metal. Copper-gold and copper-silver-gold sheet metal also figured in their repertoire.

The sounds produced by these alloys and their colors generated an entirely new sphere of experience for these people, who used them in ritual through which they communicated with the supernatural. Sixteenth-century literature makes clear that golden colors were related to the sun and silvery colors to the moon, both powerful; deities, and that the sounds of bells and other percussion instruments replicate the sounds of thunder and rain and are linked to human and agricultural fertility.

The cultural concern for the acoustical properties of metal, especially in metal bells, was uniquely West Mexican, and did not derive from Andean cosmologies. Metallic color, especially golden and silvery colors and associated with the supernatural is Pan American in scope and probably originated in Colombia. The techniques smiths used to produce these colors varied by region (Hosler 1994).

Professor Hosler and her students and collaborators also have examined the mechanisms through which these metallurgical technologies were introduced from coastal Ecuador to West Mexico. They built and sailed (on the Charles River in Boston) balsa rafts whose design characteristics had been carefully observed off the coast of Ecuador by 16th-century Italian and Spanish sailors. The Europeans noted that the rafts carried cargos of spondylous shell as well as metal objects—tweezers, rings and others as trade items to the north along the Pacific coast. The Europeans encountered this novel raft design for the first time as they sailed along coast of Ecuador (Dewan and Hosler 2008).

This work is the first comprehensive investigation of this issue and that identifies and addresses the materials, fabrication methods and design and the social contexts that structured these technologies.

Professor Hosler also has carried out in in-depth ethnotechnological study of northern Andean potters (one and a half years of field work) who made copies of Andean pottery objects: the data show that this technology reified the Andean tradition of quadripartite division: the potters occupied one side of town, the middlemen the other. High-quality pottery copies were produced in the upper quadrant, lower-quality in the lower (Hosler 1996). This study is the first to demonstrate that the principle of dual division, an entrenched Andean form of social organization, is able to manifest itself in regional economies, in this case where one segment of the town produces the goods and the other sells them, and in the process enrich themselves to the extent that endogamy by sector became the prevailing trend.

Professor Hosler, Sandra Burkett, and Michael Tarkanian carried out the original study on Mesoamerican rubber production (Science 1999). Maya peoples used large solid rubber balls in their ballgame, a widespread ritual activity that enacted their beliefs concerning the origins of the universe. Ball courts are often major constituents of Maya architectural complexes. The Olmec, who preceded the Maya, invented the rubber-processing technique wherein latex from the Mexican Castilla elastica tree was combined with the liquid from Ipomea alba—a species of morning glory vine. Castilla elastica is characterized by sulfur containing molecules that facilitate crosslinking, producing an elastic “bouncy” material that these people shaped into large heavy balls, which preceded Goodyear’s work by some 3,500 years.                                

Professor Hosler carried out a major excavation following an extensive survey of the Balsas drainage in the West Mexican states of Guerrero and Michoacán to identify copper smelting sites. In 2000 she undertook survey and mapping of La Barranca de Las Fundiciones del Manchón. This settlement was the largest identified in the survey and is located in the Sierra Madre del Sur de Guerrero at 1,500 meters. One sector contains voluminous amounts of copper slag and fragments of copper ore. Two others consist of long, solid rectangular house foundations (3-10 meters) replete with potsherds. The potsherds and habitation remains reflect an unknown ethnic or political group although the pottery forms are consistent with other Mesoamerican and West Mexican designs. Carbon-14 dates from charcoal associated with the pottery and the slag range from 1150 CE to 1750 CE. Despite these dates, there was no evidence of Spanish presence at the site—even though the region was invaded around 1521 CE or slightly later.  

The enigma presented by these data was resolved through work by Dr. Johan Garcia on 16th-century Spanish archival documents, and a re-examination of the data from one of the furnaces in the smelting area. At the invasion of Mexico, the Spanish needed to produce bronze cannons and artillery but lacked the requisite knowledge to smelt copper ores. The documents make clear that they negotiated with indigenous specialists at El Manchón and other copper smelting sites and granted them freedom from taxation and other obligations in exchange for copper ingots, which indigenous specialists smelted in a unique hybrid (Indigenous-Spanish) bellows-driven furnace capable of producing large volumes of copper metal. For several centuries following the Spanish invasion, the inhabitants of El Manchón were able to continue living at the settlement, as before, producing copper metal for Spanish consumption. Archaeological data also suggest that before the Spanish invasion the inhabitants of El Manchón were smelting copper using blowpipes and small crucibles. The likelihood is strong that they produced copper ingots, which they traded before the Spanish invasion and within Mesoamerica for items such as obsidian and other exotic goods.

Awards & Honors

Fellow, American Association for the Advancement of Science
1988 - 1998
Hennebach Visiting Professor in the Humanities, Colorado School of Mines