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MIT work revises thinking aboput peoples of ancient Mexico

In work that recasts archaeologists' thinking about peoples living in the western region of ancient Mexico, MIT researchers have shown that these people had a significant impact on other cultural groups by producing large numbers of metal artifacts and distributing them to centers as far south as Belize.

The majority of these artifacts, such as bells and tweezers, were symbols of sacred and political power. By exporting them, the West Mexican peoples not only affected economic systems but also influenced religious and ritual behavior.

"They were exporting a religious ideology," said Dorothy Hosler, associate professor of archaeology and ancient technology in the Department of Materials Science and Engineering. Professor Hosler and Andrew W. Macfarlane, a research affiliate in the department and an associate professor at Florida International University, are authors of an article on the work in the September 27 issue of Science.

West Mexican peoples were one of many cultural groups, including the Aztec and Maya, who lived in a region archaeologists call Mesoamerica. This region encompassed what is now central and southern Mexico, Guatemala, Belize, western Honduras and El Salvador. Until now, archaeologists had thought that the West Mexicans were relatively isolated and had little impact on other Mesoamerican peoples.

The new work, which links copper and bronze artifacts excavated at many sites in Mesoamerica to West Mexican ore deposits, "is the first evidence we have that West Mexican peoples were interacting intensively with other Mesoamerican groups," Professor Hosler said. "So it alters our thinking about the economic and social networks in this period [circa 1200-1521]."

In the summer of 1995 Professor Hosler spent two months in Mexico collecting ore samples from 15 deposits in West Mexico, Oaxaca and Eastern Mexico (Veracruz). With a permit granted by Mexico's National Institute of Anthropology and History, she also took samples of 171 copper artifacts from a variety of Mesoamerican archaeological sites. "I came back to MIT with boxes and boxes of artifact and ore samples," said Professor Hosler, who is also a member of the MIT Center for Archaeological Materials.

The researchers then determined the ratios of lead isotopes in each sample (isotopes of an element have different atomic weights). Lead isotope analysis, a standard technique, "can be used to identify ore sources for artifacts made from copper and copper alloys by matching the isotopic signatures of ore lead to those of the artifacts," the researchers write in Science.

Professor Hosler notes that UROP student Jennifer Pinson, now a junior in materials science, played a key role in the analysis. "She worked all last year on the project; at one point she went to Florida to hand-deliver ore samples to Professor Macfarlane because we were afraid we might lose them if we shipped them." (The samples were analyzed at Professor Macfar-lane's lab.)

The lead-isotope results showed that most of the Mesoamerican artifacts sampled were indeed made of metal smelted from West Mexican ores. These analytical data combined with historical and archaeological evidence therefore show that the West Mexicans were exporting artifacts throughout the Mesoamerican region.

Among the archaeological evidence that supports this conclusion is that "as far as we know, other Mesoamerican peoples did not develop the technical expertise to make these artifacts," Professor Hosler said. She noted that West Mexican bells, for example, are difficult to cast. "Last IAP, Professors Sam Allen, Linn Hobbs and I led a class in ancient Mexican bell casting. The students spent two weeks trying to cast copies of these bells, and we don't have it exactly right yet."

Professor Hosler concluded that although she had suspected that the West Mexicans played a major role in the production and distribution of metal artifacts, "until the lead isotope analysis we had no way of substantiating what we thought might be true."

Professor Hosler recently finished an exhibit panel on the origins and development of metallurgy in the prehistoric New World that was hung last week in Building 8 on the Infinite Corridor. For more information about MIT research on the history of materials, go to: .

The work reported in Science was supported by a grant from Grupo Mexico (Industrial Minera Mexico), American Smelting and Refining Co., and Southern Peru Copper.

A version of this article appeared in MIT Tech Talk on October 2, 1996.

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