The Psychoactive Plants Project is an ongoing, National Science Foundation (NSF) funded research program focused on the antiquity of human interactions with psychoactive plants headed by WSU researchers Dr. Shannon Tushingham (Anthropology) and Dr. David Gang (Institute of Biological Chemistry). The first phase of the project (2014–2018) focused on the development of ancient chemical residue extraction and exploring metabolomic analyses as ways of advancing methods for residue analysis. Among the outcomes of that phase of the project were the discovery of the oldest and northernmost signs of tobacco use in western North America and the development of a new method for associating ancient tobacco residues to the species level, enhancing our understanding of past plant management practices. This research has generated numerous publications, presentations, and theses and dissertations as well as significant interest from the broader public leading to coverage in a variety of outlets around the world. The second phase of the project (begun in 2019) is carrying research in ancient residue analysis forward by further refining metabolomic analytical methods and applying those methods on individuals through the analysis of residues contained in human dental calculus, while continuing to analyze ancient artifacts.
Phase 1: Human Use of Psychoactive Plants in Ancient North America: Experimental Method Development and Applications of Metabolomics Research in Archaeological Residue Analysis
The first part of the Psychoactive Plants Project was led by Shannon Tushingham (WSU Anthropology), David Gang (WSU Institute of Biological Chemistry), and Jelmer Eerkens (UC Davis Anthropology) focused on investigating human use of psychoactive smoke and drink plants—both archaeologically and in the present day. Our team developed innovative methods to identify plant compounds in archaeological pipes and other artifacts. Other accomplishments include identifying tobacco (nicotine) in multiple pipes in Washington State and Idaho, and similar collaborative research with indigenous communities in California and First Nations tribes in British Columbia.
We applied archaeometric techniques to anthropological questions about the history of human use of psychoactive plants. Contact period peoples throughout the Americas widely used plants with stimulant or hallucinogenic properties (e.g., tobacco, coffee, cacao, cassina, datura) for medicinal, ceremonial or recreational purposes, yet surprisingly little is known about their use in the past. Liquid Chromatography–Mass Spectrometry (LC-MS) and Gas Chromatography–Mass Spectrometry (GC-MS) analysis offers a direct means to track ancient use of such plants by identifying alkaloid residues in ancient artifacts. For example, our studies include work on smoke plants (in ancient pipes) and medicinal teas (in shell and pottery vessels) through identification of plant biomarkers, experimentation (“smoking” plants in experimental pipes, brewing medicinal beverages), and residue extraction from ancient specimens. A major focus has been to develop the most powerful and least destructive methods possible that will have a wide range of future applications. Archaeological applications include studies directed at understanding the cultivation, range extension, and management of tobacco in western North America. In addition to tobacco, method development included the chemical characterization of a suite of key smoke plants used by ethnographic hunter-gatherers (e.g., kinnikinnick or Arctostaphylos uva ursi, widely used by Pacific Northwest peoples) so that we may potentially identify prehistoric use of these plants. Other work has included identification of caffeine residues on shell and pottery vessels associated with Ilex vomitoria, a plant used to brew cassina, or the black drink, a caffeinated ceremonial tea famous for its use in purification rituals by elite males in the southeastern United States.
Phase 2: The Biomolecular Archaeology of Psychoactive Plants: Expanding Frontiers in Ancient Metabolomics and Dental Calculus Studies
This new phase of research, led by Drs. Tushingham and Gang, is designed to expand frontiers in the biomolecular archaeology of psychoactive plants through a 3-year program of method development. We focus on two exciting areas of research: ancient metabolomics and dental calculus studies. The research has four main objectives: (1) Improve biochemical methods of discriminating intoxicant plants to the species-level through hypothesis testing with experimental artifacts and powerful metabolomics tools involving full fingerprint chemical profiling, (2) Improve biochemical methods of identifying intoxicant plant use by humans to the individual level and to better understand uptake and preservation dynamics in ancient samples via hypothesis testing with modern dental calculus associated with users of tobacco, cannabis, opioid and other drugs, (3) Complete method validation projects through pilot studies on archaeological artifacts, (4) Expand broader impacts through educational, public, and collaborative projects. We build on previous experimental studies and archaeometric innovations, including the first recognition of nicotine in ancient calculus and metabolomic studies discriminating tobacco species in artifacts. Experiments will improve identification methods and help us better understand psychoactive plant chemistry as well as uptake and preservation dynamics of drug biochemicals in human dental calculus and archaeological artifacts. Method development involves a program of hypothesis testing and controlled laboratory-setting experimentation with produced artifacts (e.g., vessels brewed with cacao, cassina, coffee, tea), and modern dental calculus samples (obtained through a collaboration with the U. of Washington Department of Periodontics). Analytical methods include liquid and gas chromatography-time of flight mass spectrometry (LC-TOFMS and GC-TOFMS), Matrix-assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and powerful metabolomics research tools to chemically fingerprint key drug plants in experimental materials and test assumptions about ancient use of psychoactive plants.