Most of the scribes who copied the text contained in the Dead Sea Scrolls were anonymous, as they neglected to sign their work. That has made it challenging for scholars to determine whether a given manuscript should be attributed to a single scribe or more than one, based on unique elements in their writing styles (a study called paleography). Now, a new handwriting analysis of the Great Isaiah Scroll, applying the tools of artificial intelligence, has revealed that the text was likely written by two scribes, mirroring one another’s writing style, according to a new paper published in the journal PLOS One.

As we’ve reported previously, these ancient Hebrew texts—roughly 900 full and partial scrolls in all, stored in clay jars—were first discovered scattered in various caves near what was once the settlement of Qumran, just north of the Dead Sea, by Bedouin shepherds in 1946-1947. (Apparently, a shepherd threw a rock while searching for a lost member of his flock and accidentally shattered one of the clay jars, leading to the discovery.) Qumran was destroyed by the Romans, circa 73 AD, and historians believe the scrolls were hidden in the caves by a sect called the Essenes to protect them from being destroyed. The natural limestone and conditions within the caves helped preserve the scrolls for millennia; they date back to between the third century BC and the first century AD.

Several of the parchments have been carbon-dated, and synchrotron radiation—among other techniques—has been used to shed light on the properties of the ink used for the text. Most recently, in 2018, an Israeli scientist named Oren Ableman used an infrared microscope attached to a computer to identify and decipher Dead Sea Scroll fragments stored in a cigar box since the 1950s.

A 2019 study of the so-called Temple Scroll concluded that the parchment has an unusual coating of sulfate salts (including sulfur, sodium, gypsum, and calcium), which may be one reason the scrolls were so well preserved. And last year, researchers discovered that four fragments stored at the University of Manchester, long presumed to be blank, actually contained hidden text, most likely a passage from the Book of Ezekiel.

The current paper focuses on the Great Isaiah Scroll, one of the original scrolls discovered in Qumran Cave 1 (designated 1QIsa). It’s the only scroll from the caves to be entirely preserved, apart from a few small damaged areas where the leather has cracked off. The Hebrew text is written on 17 sheets of parchment, measuring 24 feet long and around 10 inches in height, containing the entire text of the Book of Isaiah. That makes the Isaiah Scroll the oldest complete copy of the book by about 1,000 years. (The Israel Museum, in partnership with Google, has digitized the Isaiah Scroll along with an English translation as part of its Dead Sea Scrolls Digital Project.)

Most scholars believed that the Isaiah Scroll was copied by a single scribe because of the seemingly uniform handwriting style. But others have suggested that it may be the work of two scribes writing in a similar style, each copying one of the scroll’s two distinct halves. “They would try to find a ‘smoking gun’ in the handwriting, for example, a very specific trait in a letter that would identify a scribe,” said coauthor Mladen Popović of the University of Groningen. Popović is also director of the university’s Qumran Institute, dedicated to the study of the Dead Sea Scrolls.

In other words, the traditional paleographic method is inherently subjective and based on a given scholar’s experience. It’s challenging in part because one scribe could have a fair amount of variability in their writing style, so how does one determine what is a natural variation or a subtle difference indicating a different hand? Further complicating matters, similar handwriting might be the result of two scribes sharing a common training, a sign the scribe was fatigued or injured, or a sign the scribe changed writing implements.

“The human eye is amazing and presumably takes these levels into account too. This allows experts to ‘see’ the hands of different authors, but that decision is often not reached by a transparent process,” said Popović. “Furthermore, it is virtually impossible for these experts to process the large amounts of data the scrolls provide.” The Isaiah Scroll, for instance, contains at least 5,000 occurrences of the letter aleph (“a”), making it almost impossible to compare every single aleph by eye. Popović thought pattern recognition and artificial intelligence techniques would be well suited to the task.