Ancient Arabians Used Psychoactive Plant 2,700 Years Ago

Archaeologists have discovered the world’s oldest evidence of people burning Peganum harmala—a psychoactive plant still used in traditional medicine today—at a 2,700-year-old oasis settlement in Saudi Arabia.

The findings, based on chemical analysis of residues found inside ancient fumigation devices, reveal that Iron Age communities in Arabia were deliberately using local plants for their therapeutic and mind-altering properties centuries before written records documented such practices. The discovery at Qurayyah oasis represents the earliest radiometrically dated material evidence of harmal being used for fumigation globally, providing unprecedented insight into ancient Arabian healing traditions that persist in the region today.

Chemistry Reveals Ancient Secrets

The research team, led by Dr. Barbara Huber from the Max Planck Institute of Geoanthropology, used high-performance liquid chromatography-tandem mass spectrometry to analyze organic residues preserved inside clay fumigation devices. The sophisticated technique detected specific alkaloids—harmine and harmane—that occur naturally in Peganum harmala.

“Our findings represent chemical evidence for the earliest known burning of harmal, not just in Arabia, but globally,” says Barbara Huber, lead author of the study published in Communications Biology.

The plant, commonly known as Syrian rue or harmal, produces compounds that act as reversible inhibitors of monoamine oxidase A (MAO-A), temporarily blocking an enzyme responsible for breaking down neurotransmitters like serotonin and norepinephrine. This biochemical action contributes to the plant’s diverse effects, ranging from sedation to stimulation.

A Domestic Practice, Not Ritual

What makes this discovery particularly significant is where the fumigation devices were found. Unlike other archaeological sites where drug plants are typically associated with religious ceremonies or burial practices, all the harmal-containing devices at Qurayyah came from residential areas—courtyards, cooking areas, and cellars of ordinary homes.

This domestic context suggests the plant was used for practical purposes rather than elaborate rituals. The researchers identified multiple potential uses: air purification and disinfection due to its antibacterial properties, pest control in the warm oasis environment, and treatment of various ailments including headaches, joint pain, and other health conditions.

Importantly, the study found that different substances were used in different contexts within the same settlement. While harmal appeared in residential fumigation devices, burial sites at nearby oases contained different aromatic substances like Commiphora and coniferous resins, indicating a clear distinction between domestic and ceremonial plant use.

Key Research Findings:

• World’s oldest evidence of Peganum harmala fumigation (2,700 years ago)
• Found exclusively in domestic contexts, not ritual or burial sites
• Chemical analysis detected harmine and harmane alkaloids in ancient residues
• Co-occurrence with plant sterols suggests use of harmal seed oil
• Different substances used for domestic versus ceremonial purposes

The Plant’s Powerful Properties

Peganum harmala demonstrates what scientists call hormesis—where small doses produce beneficial effects while larger doses can be harmful or even toxic. The plant’s alkaloids exhibit “a broad spectrum of actions on the human body,” including antibacterial, antiparasitic, and anti-inflammatory activities.

At therapeutic doses, the compounds can act as mild stimulants and mood stabilizers. At higher concentrations, they can produce hallucinations and euphoria. However, excessive consumption can lead to poisoning, with several modern cases of harmal-related toxicity already documented.

The method of administration—fumigation rather than ingestion—would have provided a controlled way to benefit from the plant’s properties while avoiding the risks of overdose associated with eating or drinking concentrated preparations.

Living Heritage Under Threat

The archaeological discovery gains added significance because similar plant-based practices continue in the region today. Among the approximately 2,250 identified plant species in Arabia, nearly 25% are documented for medicinal uses, and harmal remains part of traditional medicine in Saudi Arabia.

“This discovery shows the deep historical roots of traditional healing and fumigation practices in Arabia,” adds Ahmed M. Abualhassan, Heritage Commission co-director of the Qurayyah project. “We’re preserving not only objects, but the intangible cultural heritage of ancient knowledge that still holds relevance in local communities today.”

However, this traditional knowledge faces modern threats. “Such practices are increasingly disappearing,” the researchers note, emphasizing “the urgent need to document and preserve this rich ethnobotanical knowledge before it is lost entirely.”

Scientific Detective Work

The research required sophisticated analytical techniques because the organic compounds were preserved in minute quantities after nearly three millennia. The team used multiple reaction monitoring (MRM) mass spectrometry, which “facilitates the monitoring of specific precursor and product ion pairs, significantly enhancing the specificity and sensitivity of the analysis.”

For harmine, the technique detected specific molecular fragments: precursor ions breaking apart under controlled energy conditions to produce telltale patterns that matched reference standards. Similar patterns confirmed the presence of harmane, providing definitive chemical fingerprints of the ancient plant use.

The analysis also revealed high concentrations of plant sterols like campesterol and β-sitosterol in some samples, suggesting that harmal seeds—which are rich in oils—were the specific plant parts being burned.

Implications for Ancient Medicine

This discovery challenges assumptions about the sophistication of ancient medical knowledge. Rather than random experimentation, the evidence suggests Iron Age communities had developed systematic understanding of local plants and their effects.

“The integration of biomolecular analysis with archaeology has allowed us to identify not just what kind of plants people were using, but also where, how, and why,” says Prof. Marta Luciani, excavation director at Qurayyah and archaeologist at the University of Vienna.

The findings also suggest potential applications in modern drug discovery. As the researchers note, “utilizing the information stored in ancient organic remains could enable the recovery of bioactive compounds that have been forgotten over time, potentially leading to the development of innovative plant-based therapies.”

Beyond pharmacology, the research provides crucial documentation of cultural practices that bridge ancient and modern Arabia, offering insights into how traditional knowledge systems develop and persist across millennia of human experience.