Institute of Maya Studies

Soil Biomarkers of Cacao Tree Cultivation in the Sacred Cacao Groves of the Maya

with Richard E. Terry Ph.D. and emeritus Professor of Soil Science
Brigham Young University

The importance of cacao in ancient Mesoamerica is attested by the presence of cacao biomarkers in ritual pottery. By at least the Postclassic period, if not earlier, cacao beans are thought to have been a prominent mode of currency in central Yucatan. During the colonial period the Maya of Yucatan were tending sacred groves of cacao trees in the shaded, humid microclimates of karst sinkholes that dot the peninsula. We report on the development of a method for the extraction and quantitation of the methylxanthine biomarkers of cacao (theobromine, theophylline, and caffeine) from soil. The presence of these biomarkers provides evidence of the distribution and ritual importance of these sacred cacao groves to the Maya. Methylxanthine biomarkers were present in the soils of nine of eleven sampled sinkholes in Yucatan and Quintana Roo, MX.

We adapted our hot water extraction protocol for the extraction and measurement of methylxanthine biomarkers from Fremont culture pottery found in San Juan County, Utah dating to approximately 1000 AD. The pottery was collected at the ruins of Montezuma Village in Montezuma Canyon. Cacao does not grow in the hot desert climate of southeast Utah, therefore the cacao was likely grown in Mesoamerica and carried by merchants all the way to Utah.

Richard Terry at Tikal
Richard E. Terry
is Professor Emeritus of Soil Science from Brigham Young University, Provo, Utah. In 1972 Dr. Terry received his B.S. degree in Agronomy from Brigham Young University. He completed M.S. and Ph.D. degrees in Soil Biochemistry from Purdue University in 1974 and 1977, respectively. In 1977 he became Assistant Professor of Soil Science at the University of Florida, Everglades Experiment Station at Belle Glade, Florida. He conducted research on the microbial transformations carbon and nitrogen in the peat soils of the Everglades. He and his colleagues conducted some of the early research on the emissions of the atmosphere warming gases, carbon dioxide and nitrous oxide, from the undrained wetlands and the drained agricultural fields of the Everglades.

In 1980 Dr. Terry joined the Soil Science faculty of Brigham Young University. He taught soil science and environmental science courses. He mentored undergraduate and graduate students in field and laboratory research on the microbial cycles of carbon and nitrogen in soils and water.

In 1997 he began a collaboration with Geographer, Dr. Perry Hardin and Archaeologist, Dr. Stephen Houston on the sampling and analysis of chemical residues deposited in the soils and floors of ancient Maya activity areas at the site of Piedras Negras, Guatemala. In the subsequent 20 years his soil research in the Maya area expanded beyond extractable phosphorus, plant nutrients and heavy metals to include Stable carbon isotope work to help identify ancient corn fields. Most recently he and his students have developed procedures for the extraction of the biomarkers of cacao tree production from soils and the HPLC-MS quantitation of theobromine, theophylline, and caffeine in soil extracts.

Dr Terry has collaborated with more than 40 prominent archaeologists in the design of soil sampling protocols for the chemical analyses of human activity areas and for the identification of ancient maize fields and cacao orchards. He and his students conducted soil research at 28 ancient Maya sites in Mexico, Belize, Guatemala, Honduras, and El Salvador. Their research has resulted in 55 articles in archaeological and soil science journals and scholarly books.