November 24, 2018 – 2:00 PM: R.A. Varney and Linda Scott Cummings

Chocolate, Mayans, and Climate Models

Chocolate was not only “Food of the Gods” and used as currency, it was both an everyday and a ritual beverage. Access to chocolate (Theobroma cacao) throughout the Mayan empire cannot be determined based solely on modern locations. Cacao trees’ sensitivity to environmental conditions, specifically available water, controlled distribution of this valuable resource throughout history and today. Requirements include temperatures staying within the range 20–30 C, with no longer than a 3-month period with less than 100mm rainfall. Trees grow well in shady areas. Today their preferred habit appears to be deep, fertile sediments of river valleys with heavy humidity (more than 90%). Likely, these restrictive environmental requirements enhanced cacao’s monetary value in the past, as not all communities were located in close proximity to areas where cacao grew. Indeed, wars were fought to control the best cacao-growing territories. Recovering direct evidence of cacao from archaeological sites is difficult. Modeling past climate, including monthly precipitation values, and mapping the models over the Mayan region identifies areas of interest that might have supported cacao growth. Comparison of these locations with modern distribution of cacao sheds additional light on the possible importance of this resource during the florescence, growth, and subsequent decline of the Mayan civilization.


R. A. Varney, paleoecologist, has worked for PaleoResearch Institute since 2003. He attended graduate school in Arizona, studying with C. Vance Haynes. At PRI his responsibilities are many. He is co-developer of the microscopic charcoal recovery technique for AMS radiocarbon dating. He extracts microscopic remains from samples, counts pollen, and is responsible for all chemical pre-treatment of radiocarbon samples. He works as part of the team to develop new techniques for radiocarbon sample chemical treatments. His particular interests include; climate change, especially at the end of the Pleistocene; scientific method development, archaeological chemistry, and climate modeling of the past. R.A. worked in West Stoneham Pasture Archaeological district in northeastern Colorado, and worked at the Dent Site re-evaluation and Hell Gap. He participated in the archaeological survey of Rocky Mountain Park and excavated at Caribou Lake. In 2012 he was responsible for sample collection at the Laetoli Footprint site in Tanzania.