Following an Asphalt Trail to Ancient Olmec Trade Routes

Abstract

SOCIETY FOR AMERICAN ARCHAEOLOGY MEETING > SOCIETY FOR AMERICAN ARCHAEOLOGY, 26–30 MARCH 2008, VANCOUVER, CANADA ![Figure][1] Sticky success. Digging asphalt from a seep, researchers recreated samples of Olmec sealant ( inset ). CREDIT: CARL J. WENDT When archaeologists teach about the Olmec culture, they flash images of massive stone heads, sculpted for a sophisticated elite who ruled the swampy lowlands of Mexico from 1200 to 400 B.C.E. But a poster by archaeologist Carl Wendt of California State University, Fullerton, throws the spotlight on Olmec commoners. Once dismissed as simple maize farmers, the ordinary Olmec apparently mastered a sophisticated technique for making asphalt, crucial to sealing wooden boats, and they traded the valuable substance to others. This research will shed new light on previously invisible trade routes, says Olmec expert David Grove of the University of Florida, Gainesville. Because Wendt can distinguish asphalt from various sources, Grove notes, the work “adds a significant new ‘artifact’ [asphalt] to the small list of artifacts that can be used in the study of trade in Mesoamerica at 1000 B.C.E.” Earlier archaeologists paid little attention to asphalt, occasionally noting its presence on sacred figurines, tool handles, and potsherds. But during excavations at the Olmec site of Paso los Ortices, Wendt discovered a pit containing 250 kilograms of asphalt slabs. He wondered how the Olmec processed asphalt, what they used it for, and whether elites controlled its manufacture. To find out, his team studied thin sections of asphalt lumps from Olmec sites with a petrographic microscope. They noted even patterns of sand particles and impressions of decomposed plants, suggesting that these silica-rich materials were intentionally mixed in during heating to add structure to the asphalt. The team also identified and sampled more than 50 asphalt seepages in the Olmec region. Then they experimented, adding different plant additives and heating samples in clay pots over fires to produce an asphalt that was both flexible enough to apply to figurines and other objects and yet hard enough to resist melting in the sun. “We had a bear of a time trying to get it to that state,” says Wendt. Some samples were simply too watery. But Wendt and his team processed other, stickier samples in just a few hours; they found that the leaves of a plant the local inhabitants use to wrap tamales produced the best asphalt. The result is a very early example of materials processing, says Philip Arnold, an archaeologist at Loyola University in Chicago, Illinois, and it's “like a culinary art: You have to understand the properties of individual ingredients and how they work together.” Wendt's evidence now suggests that commoners produced their own asphalt, because the seeps were too numerous for easy management by Olmec lords. Moreover, Wendt's studies at the small Olmec site of El Remolino, dated between 1200 and 850 B.C.E., revealed that commoners extensively processed and used asphalt in their households. But what did they use it for? Other emerging data provide some clues. In January on the Veracruz coast, a team led by Alfredo Delgado Calderon of the Instituto Nacional de Anthropologia e Historia, Veracruz, unearthed remains of a 2200-year-old port and two canoes. The wood had rotted away, but the team found a 1- to 8-centimeter- thick asphalt lining that had once sealed the entire interior of the canoes. Wendt suggests that Olmec commoners processed asphalt primarily to waterproof their boats. That idea fits well with new thinking about the Olmec. For years, archaeologists had agreed that the Olmec economy was founded on maize agriculture, but recent studies reveal that the Olmec situated their villages along rivers and hunted wetland game. “Rivers are their transportation, communication, and trade routes,” says Wendt. “So to have effective watercraft is going to be critical.” Wendt is now studying the Olmec trade in asphalt, using chemical analyses to trace samples to their seepage of origin. This “provides a wonderful economic geography that has not been available for Olmec studies,” says Arnold. “It helps us to contour the Olmec political economy.” [1]: pending:yes