If you’re not familiar with the fierce, often naked, and always crazy berserker warriors, well…they are the reason we say that someone “went berserk.”

They struck fear into pretty much everyone during the Viking Age, and though scientists have always assumed they used some kind of mind-altering substance to reach the savage, trance-like state that allowed them to feel no fear or pain in battle, no on was exactly sure what it was they took.

Some have long posited that psychedelic mushrooms were the secret sauce, but a recent study suggests they might have relied on something else –  a lesser known herb called henbane (Hyoscyamus niger).

Ethnobotanist Karsten Fatur explains in her article in the Journal of Ethnopharmacology why henbane is a more plausible suspect than the mushrooms, drunkenness, mental illness or psychosis borne from the fungal disease ergotism.

Henbane is native to the Mediterranean, but was introduced to Scandinavia during the Roman Iron Age. The presence of the seeds at a number of Viking-age settlements in Denmark and Finland suggest they were easy to get and widely used from the time of the Middle Ages forward.

It’s an effective pain killer, and it also produces a psychedelic state like the one of pure rage described the berserkers going into before battle. According to the study,

“This anger effect can range from agitation to full-blown rage and combativeness depending on the dosage and the individual’s mental set. As this is perhaps the most defining component of the berserker state, this symptom is of central importance in identifying potential causes and provides a very critical reason as to why H. niger is a more appropriate theoretical intoxicant for the berserkers than A. muscaria.

In addition, reports state that the berserkers were frequently so blinded by rage that they were unable to distinguish between enemy and ally during battle – and an inability to recognize faces is a known symptom of henbane and drugs like it.

The after effects berserkers describe – basically a hangover – also line up, Fatur argues, and mushrooms just don’t typically cause any trouble the morning after.

There are other aspects of their behavior, like biting their shields and chattering their teeth, that are still unexplained.

But I mean, maybe they were just dudes who were high as f*ck and looking for a (naked?) fight.

They won’t be the last, I reckon.