Caligula, the notoriously erratic Roman emperor known for his bloodthirsty cruelty, probably also possessed a nerd’s knowledge of medicinal plants, according to a new Yale study.

The study, by the Yale Ancient Pharmacology Program (YAPP), illuminates a brief anecdote about Caligula originally reported by the historian Suetonius in “The Twelve Caesars,” a second-century collection of biographies of Roman rulers from Julius Caesar to Domitian.

In the story, an unnamed Roman senator of praetorian rank who is suffering from an unspecified ailment takes a leave of absence to the Greek spa town of Antikyra in  hopes that his health will benefit from treatments made from hellebore — a flowering plant purported to have medicinal properties. The senator, perhaps pressing his luck, asks Caligula to extend his leave. In response, the emperor has the hapless senator executed, quipping that “a bloodletting was necessary for one whom hellebore had not benefited in all that time.”

Yale scholars, combining ethnobotanical field data and a close reading of ancient texts, offer new understanding of the passage, providing context about Antikyra’s place in the Roman Empire and Caligula’s familiarity with pharmacology.  

“Our work suggests that Antikyra functioned as a kind of Mayo Clinic of the Roman world — a place where affluent and influential Romans visited for medical treatments not widely available elsewhere,” said co-author Andrew Koh, who is YAPP’s principal investigator and a research scientist at the Yale Peabody Museum. “It also provides evidence that Caligula, while a tyrant, was more knowledgeable about medicine than has been previously understood.”