ARCHAEOLOGY
A chocolate habit in ancient North America By Michael Bawaya
PHOTO: NATIONAL MUSEUM OF THE AMERICAN INDIAN, SMITHSONIAN INSTITUTION [052109.000 (RIGHT) 052116.000 (LEFT)], PHOTO BY WALTER LARRIMORE
F
or centuries, elite people in ancient Mesoamerica drank a foaming beverage made from the ground beans of the tropical Theobroma cacao tree. Served in cylindrical jars and spouted pitchers, this was a chocolate drink steeped in ritual. Priests prepared the beverage in religious ceremonies, and in their great cities in present-day Mexico and Central America the Maya honored the cacao god Ek Chuah. North America had its great prehistoric cities, too—for example, ancient Cahokia near St. Louis, Missouri, or Chaco Canyon in New Mexico—but for years most archaeologists assumed little contact between the cultures. Chocolate may change that picture, with the recent discovery of subtle residues of it in pots from Cahokia. Added to similar evidence from the Southeast and Southwest, the findings suggest regular trade in cacao—and movements of the people who imbued it with significance— between ancient Mesoamericans and their northern neighbors, says Dorothy Washburn, an archaeologist at the University of Pennsylvania Museum of Archaeology and Anthropology and co-author of a new paper, published online last month. But the new work also reveals the complexities of such residue analysis, she says. “The separation of archaeology north and south of the border is a political reality but a historical fiction,” says archaeologist Stephen Lekson of the University of Colorado, Boulder, who has long argued for contact between the cultures. “If we needed a final nail, cacao shows us that ancient civilizations north of the border were deeply and significantly connected to the civilizations of Mesoamerica.” Though some Mesoamerican artifacts have turned up in the Southwest, the evidence for contact between these two centers of pre-Columbian culture is scant. Many archaeologists believed that few interactions took place across the thousands of kilometers of desert and mountains dividing them. Then, in 2009, researchers reported cacao residue on sherds of cylinder jars from Chaco Canyon. A few years later, Washburn and her husband William, who was then a chemist at Bristol-Myers Squibb, reported that they had detected theobromine, a telltale alkaloid biomarker in T. cacao, in about 50 vessels from great house pueblos in Chaco
Chemical residues from chocolate turned up in these pots from Chaco Canyon in New Mexico.
Canyon and from Los Muertos, a Hohokam site in southern Arizona. But many archaeologists, skeptical that consumption of this elite beverage was so prevalent, assumed that the jars were contaminated. In their new paper, in the Journal of Archaeological Science, the Washburns and their colleagues report finding some contamination in the 123 vessels they analyzed, from sites in the Southwest, Southeast, and Midwest dating from 900 to 1400 C.E. They rinsed the ancient ceramics and analyzed the solution for three alkaloids from T. cacao—theobromine, caffeine, and theophylline. As controls, they tested pots from times and places where prehistoric cacao usage was extremely unlikely and also sampled dust from the museum shelves where the vessels were stored. Most vessels had at least a low level of theobromine, which the Washburns attribute to airborne contamination: People today consume so much chocolate and coffee (which contains the same alkaloids) that traces of this molecule are everywhere. Thus, theobromine’s mere presence or absence in a pot is not conclusive, Dorothy Washburn says. But the team found that roughly onethird of the vessels, including 17 from the Southeast and Midwest—and none of the controls—contained significantly higher
SCIENCE sciencemag.org
levels of theobromine, which they attribute to ancient cacao. The team also studied regional plant databases to make sure that no nearby plants contained theobromine. One Southeastern holly, Ilex vomitoria, does, and it was brewed in a tea by ancient people. But cacao has a different alkaloid signature than I. vomitoria, with more theobromine than caffeine, so the team says that pots with that higher ratio must have held chocolate. Added to other lines of evidence for contact, such as Mesoamerican-style platform mounds near Cahokia and ball courts in the Southwest, the cacao residues show robust interaction and a transfer of “ritual concepts” between peoples, Washburn argues. Some researchers find the new evidence impressive. “It’s an important paper,” says Steve Wolverton, an archaeologist at the University of North Texas, Denton, who specializes in applying analytical chemistry to archaeology. He noted that there’s still a chance that an unknown plant containing theobromine left its mark on the ceramics. But he considers contact between the regions plausible. Others are doubtful. There are just too many vessels with purported cacao, says archaeologist Timothy Pauketat of the University of Illinois, Urbana-Champaign. The drink is thought to have been reserved for the privileged, yet most of the North American vessels said to have cacao residue come from the hinterlands of Cahokia. He doesn’t rule out contact, however: “I will not be surprised if we do find chocolate in a few pots from, say, Cahokia, at some point in the future,” he says. But for now, “we have not one bean.” Washburn and Lekson acknowledge that the Mesoamerican palaces were a long way from the grand structures of Chaco and Cahokia. But in their view, ancient Americans could and did travel those distances. Says Lekson: “Before colonial wars, it was all one continent.” ■ Michael Bawaya is the editor of American Archaeology. 29 AUGUST 2014 • VOL 345 ISSUE 6200
Published by AAAS
991
Downloaded from www.sciencemag.org on August 28, 2014
Residues on pottery suggest close ties between Mesoamerica and cultures to the north
A chocolate habit in ancient North America By Michael Bawaya
PHOTO: NATIONAL MUSEUM OF THE AMERICAN INDIAN, SMITHSONIAN INSTITUTION [052109.000 (RIGHT) 052116.000 (LEFT)], PHOTO BY WALTER LARRIMORE
F
or centuries, elite people in ancient Mesoamerica drank a foaming beverage made from the ground beans of the tropical Theobroma cacao tree. Served in cylindrical jars and spouted pitchers, this was a chocolate drink steeped in ritual. Priests prepared the beverage in religious ceremonies, and in their great cities in present-day Mexico and Central America the Maya honored the cacao god Ek Chuah. North America had its great prehistoric cities, too—for example, ancient Cahokia near St. Louis, Missouri, or Chaco Canyon in New Mexico—but for years most archaeologists assumed little contact between the cultures. Chocolate may change that picture, with the recent discovery of subtle residues of it in pots from Cahokia. Added to similar evidence from the Southeast and Southwest, the findings suggest regular trade in cacao—and movements of the people who imbued it with significance— between ancient Mesoamericans and their northern neighbors, says Dorothy Washburn, an archaeologist at the University of Pennsylvania Museum of Archaeology and Anthropology and co-author of a new paper, published online last month. But the new work also reveals the complexities of such residue analysis, she says. “The separation of archaeology north and south of the border is a political reality but a historical fiction,” says archaeologist Stephen Lekson of the University of Colorado, Boulder, who has long argued for contact between the cultures. “If we needed a final nail, cacao shows us that ancient civilizations north of the border were deeply and significantly connected to the civilizations of Mesoamerica.” Though some Mesoamerican artifacts have turned up in the Southwest, the evidence for contact between these two centers of pre-Columbian culture is scant. Many archaeologists believed that few interactions took place across the thousands of kilometers of desert and mountains dividing them. Then, in 2009, researchers reported cacao residue on sherds of cylinder jars from Chaco Canyon. A few years later, Washburn and her husband William, who was then a chemist at Bristol-Myers Squibb, reported that they had detected theobromine, a telltale alkaloid biomarker in T. cacao, in about 50 vessels from great house pueblos in Chaco
Chemical residues from chocolate turned up in these pots from Chaco Canyon in New Mexico.
Canyon and from Los Muertos, a Hohokam site in southern Arizona. But many archaeologists, skeptical that consumption of this elite beverage was so prevalent, assumed that the jars were contaminated. In their new paper, in the Journal of Archaeological Science, the Washburns and their colleagues report finding some contamination in the 123 vessels they analyzed, from sites in the Southwest, Southeast, and Midwest dating from 900 to 1400 C.E. They rinsed the ancient ceramics and analyzed the solution for three alkaloids from T. cacao—theobromine, caffeine, and theophylline. As controls, they tested pots from times and places where prehistoric cacao usage was extremely unlikely and also sampled dust from the museum shelves where the vessels were stored. Most vessels had at least a low level of theobromine, which the Washburns attribute to airborne contamination: People today consume so much chocolate and coffee (which contains the same alkaloids) that traces of this molecule are everywhere. Thus, theobromine’s mere presence or absence in a pot is not conclusive, Dorothy Washburn says. But the team found that roughly onethird of the vessels, including 17 from the Southeast and Midwest—and none of the controls—contained significantly higher
SCIENCE sciencemag.org
levels of theobromine, which they attribute to ancient cacao. The team also studied regional plant databases to make sure that no nearby plants contained theobromine. One Southeastern holly, Ilex vomitoria, does, and it was brewed in a tea by ancient people. But cacao has a different alkaloid signature than I. vomitoria, with more theobromine than caffeine, so the team says that pots with that higher ratio must have held chocolate. Added to other lines of evidence for contact, such as Mesoamerican-style platform mounds near Cahokia and ball courts in the Southwest, the cacao residues show robust interaction and a transfer of “ritual concepts” between peoples, Washburn argues. Some researchers find the new evidence impressive. “It’s an important paper,” says Steve Wolverton, an archaeologist at the University of North Texas, Denton, who specializes in applying analytical chemistry to archaeology. He noted that there’s still a chance that an unknown plant containing theobromine left its mark on the ceramics. But he considers contact between the regions plausible. Others are doubtful. There are just too many vessels with purported cacao, says archaeologist Timothy Pauketat of the University of Illinois, Urbana-Champaign. The drink is thought to have been reserved for the privileged, yet most of the North American vessels said to have cacao residue come from the hinterlands of Cahokia. He doesn’t rule out contact, however: “I will not be surprised if we do find chocolate in a few pots from, say, Cahokia, at some point in the future,” he says. But for now, “we have not one bean.” Washburn and Lekson acknowledge that the Mesoamerican palaces were a long way from the grand structures of Chaco and Cahokia. But in their view, ancient Americans could and did travel those distances. Says Lekson: “Before colonial wars, it was all one continent.” ■ Michael Bawaya is the editor of American Archaeology. 29 AUGUST 2014 • VOL 345 ISSUE 6200
Published by AAAS
991
Downloaded from www.sciencemag.org on August 28, 2014
Residues on pottery suggest close ties between Mesoamerica and cultures to the north
