The legendary Viking warriors known as berserkers were renowned for their ferocity in battle, purportedly fighting in a trance-like state of blind rage (), howling like wild animals, biting their shields, and often unable to distinguish between friend and foe in the heat of battle. But historians know very little about the berserkers apart from scattered Old Norse myths and epic sagas.
One intriguing hypothesis as to the source of their behavior is that the berserkers ingested a specific kind of mushroom with psychoactive properties. Now an ethnobotanist is challenging that hypothesis, suggesting in a recent paper in the Journal of Ethnopharmacology that henbane is a more likely candidate.
Accounts of the berserkers date back to a late ninth-century poem to honor King Harald Fairhair. The 13th-century Icelandic historian/poet Snorri Sturluson described Odin’s berserkers as being “mad as dogs or wolves” and “strong as bears or wild oxen,” killing people with a single blow. Specific attributes can vary widely among the accounts, often veering into magic or mysticism. There are claims that berserkers were not affected by edged weapons or fire, but they could be killed with clubs. Other claims say they could blunt the blades of their enemies with spells or just by giving them the evil eye. Most accounts at least agree on the primary defining characteristic: a blind ferocious rage.
The onset of purportedly began with bodily chills, shivering, and teeth chattering, followed by swelling and reddening of the face. Then the rage broke out, and once it abated, the berserker would experience both physical fatigue and emotional numbness for a few days. Several hypotheses have been proposed for why the warriors would have behaved this way, including self-induced hysteria—aided by biting their shields and howling—epilepsy, ergot poisoning, or mental illness. One of the more hotly contested hypotheses is that the berserkers ingested a hallucinogenic mushroom (), commonly known as fly agaric, just before battle to induce their trance-like state.
has a distinctly appearance, with its bright red cap and white spots. While it’s technically toxic to humans, the mushrooms are apparently safe to ingest after parboiling them twice. was very popular as an intoxicant among Siberian tribes, possibly holding religious significance because of its psychoactive properties. The latter aspect is due to two compounds: ibotenic acid and muscimol, with muscarine (first discovered in 1869) most likely responsible for some of the more unpleasant side effects. The ‘shroom typically induces a drunken state with auditory illusions and shifts in color vision. It can also induce vomiting, hyperthermia, sweating, reddening of the face, twitching and trembling, dilated pupils, increased muscle tone, delirium, and seizures.
Much of that is consistent with accounts of berserker behavior. But according to Karsten Fatur, an ethnobotanist at the University of Ljubljana in Slovenia, henbane () is a much better candidate. It’s been around since ancient Greece and has been used in various cultures throughout history as a narcotic, painkiller, cure for insomnia, and anesthetic. It’s a common treatment for motion sickness and can produce short-term memory loss. It can knock out someone for 24 hours, and in rare cases henbane can lead to respiratory failure. It’s also been investigated as a possible truth serum. Henbane even found its way into early European beers, gradually being replaced with hops after the passage of the Bavarian Purity Law in 1516.
Fatur argues that while both the mushrooms and henbane could account for increases in strength, altered consciousness, delirium, jerking and twitching, and red face commonly associated with the berserkers, aggressive rage is not common with the mushroom. Fatur cites several cases involving angry behavior associated with plants related to henbane, containing the same alkaloids.
“This anger effect can range from agitation to full-blown rage and combativeness depending on the dosage and the individual’s mental set,” he wrote. “As this is perhaps the most defining component of the berserker state, this symptom is of central importance in identifying the potential causes and provides a very critical reason as to why is a more appropriate theoretical intoxicant for the berserkers than .”
Henbane can also dull pain (hence the accounts of berserkers being nearly invulnerable), contribute to an inability to recognize faces, cause removal of clothing, and lower blood pressure, which Fatur suggests might account for the assertion that berserkers didn’t lose much blood when injured with blades. And berserkers purportedly suffered from numerous side effects for several days following that battle high. The mushrooms typically don’t produce lingering side effects; henbane does, including headache, dilated pupils, and blurred vision.
Fatur suggests that would have been much more rare in Scandinavia—it typically grows in forests since it flourishes in a symbiotic relationship with tree roots. Henbane, in contrast, grows rapidly as a weed and is known to have flourished in Scandinavia during the berserker era. And a woman’s grave in Denmark, dating back to about 980, included a pouch of henbane seeds, along with clothing and jewelry, according to Fatur.
Naturally, a few caveats are in order. There are elements of berserker behavior that henbane cannot account for, such as the biting of shields and chattering teeth. And Fatur notes that much of this is speculative, since there simply isn’t sufficient archaeological or historical evidence to prove or disprove his hypothesis. He himself has no specific expertise in history or archaeology, so the ethnobotanist is calling on future research by those communities to confirm or disprove his unique ethnobotanical perspective.