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Engineers Dig Archeology

Dorothy Hosler and her students approach archeology as engineers, bringing to light new information about ancient civilizations.
November 1, 2004

Dorothy Hosler still remembers the hot spring afternoon in 1998 when she hiked into the remote mountains of Guerrero, Mexico, and found what she had been seeking for four months: the first known pre-Columbian metalworking site north of Ecuador, inhabited sometime after 1100 c.e. Hosler, a professor of archaeology and ancient technology at MIT, and two villagers had been traveling for hours by jeep, horseback, and foot to reach the site, which was nestled in a forest high in the mountains. She had already scouted dozens of archaeological sites, but to no avail. Her guides assured her that their destination, El Manchon, was special, but she wasnt entirely persuaded. I had been on many dead-end trips with people who said, Theres something you absolutely have to see, and wed get way out in the middle of nowhere and there wouldnt be anything. So I had no expectations, Hosler says.

When they finally arrived, Hoslers doubts faded. She found a wooded site littered with pottery shards and obsidian, a shiny, black volcanic glass used for making tools. She saw 36 mounds in two areas, the longest stretching up to 22 meters and about two or three meters high, that were obviously human made. Hoslers guides led her across a stream to a large clearing. Seven or eight circular stone ruins, each about a meter and a half in diameter, lay scattered under the open sky. Hosler guessed that they were furnaces used to draw copper out of ore. Slag, a brittle by-product of smelting, covered the ground and snapped underfoot as she surveyed the site. I thought, I cant believe what Im seeing. I must be imagining this, she recalls. Hosler knew she had hit the jackpot. The slag was a clear indication that smelting had taken place, and the pottery shards and ruins of buildings led her to believe that the site was indeed pre-Columbian. It took years of delicate negotiations with government officials, but she finally obtained permission in 2001 to excavate the site and has been going back every summer since. Hosler hopes her ongoing excavation will answer technical questions about the smelting process and also help explain the cultural and religious role of metalworking in ancient Mexican societies.

Hoslers search for El Manchon brought much of the pain and pleasure archaeologists typically encounter while hunting down the ideal site. But her experience was made atypical by her expertise in metallurgywhich few archaeologists possessand access to a laboratory devoted to the analysis of archaeological materials. In fact, just after Hosler returned from Mexico, the Department of Materials Science and Engineering began to offer a doctoral program in archaeological materialsthe only program of its kind in the world. At the same time, it created an experimental undergraduate program in archaeology and materials, which became an official major in fall 2004. The aim of the program is to teach archaeology from the perspective of engineering. Although its increasingly common for archaeologists to have backgrounds in chemistry, biology, or geology, Hosler says, few are trained in engineering. But if they were, they would have the tools to answer not only the what, where, when, and who about a particular site or artifact but also the how and why of an artifacts creation. Applying an engineers perspective opens up an enormous field of inquiry, says Hosler. There are so many problems that havent even been approached. Hosler and her students have already broken new ground by examining the technical choices ancient people made when, for example, constructing a raft or making a rubber ball. Such choices help define cultures, Hosler says, which are exactly what archaeologists struggle to understand.

The Perfect Site

Over the last three years, Hosler and her students have spent months excavating structures and studying materials at El Manchon to answer questions about how pre-Columbian Mesoamericans smelted. Its an area not well understood, but Hosler believes that understanding the metal-making process can shed light on, among other things, the values indigenous peoples held. For example, by analyzing the chemical composition of the slag, Hosler can get a picture of the kind of metalits color and strength, for examplethat indigenous peoples preferred. Chemical analysis also provides clues to the type of ore favored and the temperature at which it was processed. By piecing the clues together, Hosler is already drawing some preliminary conclusions about how the people of El Manchon used their resources. Her analysis shows significant amounts of copper in the slag. In other cultures, slag is typically reprocessed to extract the remaining bits of copper. But the people of El Manchon appear to have only processed the ore once. Hosler guesses that the ore in the area was so rich in copper that it did not require reprocessing.

In addition to studying exactly how pre-Columbian Mesoamericans smelted ore, Hosler hopes to answer larger questions about the lives of indigenous metalworkers in Mexico. Evidence at El Manchon indicates that people lived very close to the smelting site year round. Hosler found residential buildings littered with broken pieces of cookware and other domestic pottery, which would most likely not have been present at a site used only by seasonal workers. Hosler also unearthed a perplexing structure that appears to have had religious significance. The building has nine mysterious holes in the floor and houses a stela, a vertical rock that was for Mesoamerican people a religious symbol. A small pot beneath the stela probably accommodated a religious offering that could be burned. Hosler says its unusual for a religious building to be right in the middle of a loud, dirty industrial area, and she is excited to study the structure further. Its one of a kind, she says. Its like nothing Ive ever seen.

Rafts and Rubber

In addition to excavating sites in Mexico, Hosler and her students are creating objects to test their theories about the construction techniques of ancient peoples, which ultimately provide insight into how they lived. Her work has inspired a wide range of student research projects, including efforts to built an Ecuadorian raft similar to those encountered by the Spanish during their conquest of northern South America and to discover how ancient Mexicans made rubber balls.

The raft project was an outgrowth of Hoslers previous studies on how metallurgy came to Mexico. After conducting detailed studies on hundreds of pre-Columbian Mexican metallic artifacts, she now believes that metalworking was brought to Mexico from two areas: one that included modern Ecuador, Peru, and Bolivia, and another that consisted of lower Central America and Colombia.

One theory is that Ecuadorians sailed north on rafts to exchange goods with early Mexicans. During her freshman seminar last spring, Hosler says, she told her students, Somebody tried to build one of these rafts, but it sank. Since youre MIT students, I bet your raft wouldnt sink. Within about three weeks, I had four or five volunteers.

Leslie Dewan 06, Ryan Bavetta 07, Danny Shen 05, and Daniel Cohen 06 managed to build a four-meter-by-four-meter raft in only a month on a budget of just $600. The students originally wanted to build the raft, which they dubbed PakpakaQuechua for little red owlout of balsa wood, but budget constraints forced them to compromise. Instead, they made logs out of chunks of Styrofoam covered in plywood. Its the same springiness, the same stability, and the same density as balsa wood, says Dewan, a nuclear-engineering major. The students used some 500 meters of rope to lash the Styrofoam logs together. Instead of the traditional cotton, they made the sail out of synthetic fabric left over from the creation of the Daedalus, an MIT-built, human-powered airplane that flew from Crete to Santorini in 1988.

In early August, Hosler and the students successfully launched and sailed the raft on the Charles River, cheered on by a crowd of students, faculty, and staff. The process of building and sailing the raft taught the students about some of the technical challenges the ancient sailors facedfor example, how to tie together the logs with rope, and how to use centerboards to steer the craft. Dewan, who has decided to minor in archaeology and materials, will continue the project this fall, using nautical-design software to simulate how six different types of ancient rafts move through the water. She intends to use the software to help determine which raft would be the best candidate for a sail from Ecuador to Mexicoan experiment Hosler hopes to conduct next summer.

Hoslers teaching spawned yet another research project. One day, in class, she described a ball game that had been popular throughout ancient Mesoamerica. Players volleyed a large rubber ball around a stone court and through a hoop. In some cases, the losing team was decapitated as part of a religious ritual. Michael Tarkanian 00, SM 03, asked Hosler how the balls were made. Professor Hosler said no one has ever worked on that, or even thought about it, he recalls.

That question drove Tarkanian to spend much of his time as an undergraduate and as a masters student piecing together a recipe. During his freshman year, he got firsthand information from Mexicans who had made rubber balls out of latex from rubber trees when they were children. After being mixed together with juice from a species of morning glory vine, the milky latex formed a solid rubber ball. As a graduate student, Tarkanian brought liters of latex and meters of morning glory vines to MIT, where he figured out how different combinations of the two would affect the mechanical properties of the rubber. For instance, some combinations resulted in tougher rubber, which may have been useful in making shoes, and others resulted in more bouncy rubber, which could have been better for the balls. Now, as a research affiliate in the archaeology and materials program, Tarkanian is using cutting-edge software to model the ball motion and figure out how the game may have been played. For instance, Tarkanian wants to determine where players would have to stand on the court in order to be physically able to volley a five-kilogram ball through a hoop.

Although it may seem unusual to devote seven years to studying a particular kind of rubber ball, Tarkanians experience is typical. We go to enormous lengths to get one little tiny bit of information, says Hosler. And in some cases, one little piece of information can totally repudiate theories that took decades to develop. Its very exciting, Hosler says. Its the way creative work should be, because we cannot take anything for granted. Its impossible to be too wedded to any particular theory, because the data speak, and they tell stories that are not necessarily the same things that archaeologists would like the data to tell us. Hosler is confident that, by approaching questions from the point of view of engineers, she and others in the MIT program will dig up a wealth of new information about ancient civilizations, one piece of data at a time.

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