5 Mysterious Writing Systems That No One Has Deciphered

Among the most studied and most frustrating undeciphered scripts is Linear A, used by the Minoan civilization between roughly 1800 and 1450 B.C. Found on clay tablets, libation tables and other artifacts across Crete, the script resembles Linear B, which was deciphered in the 1950s as an early form of Greek.

Linear A follows patterns similar to Linear B. “We can tell that most Linear A tablets are administrative records recording things such as people, places and commodities,” says Brent Davis, associate professor of archaeology and ancient Egyptian at the University of Melbourne. He points to recurring formats that track goods and labor but says, “We can’t tell specifically what the tablets are saying.”

A major obstacle is the nature of the surviving material. Most Linear A inscriptions are only a few lines. Without longer texts, experts lack the repetition needed to identify grammar or test hypotheses. “The brevity of most inscriptions keeps us from figuring out much of the grammar of the language behind the script,” Davis notes, emphasizing how much context is missing.

Like Linear A, the challenge with the Indus script, used by the Indus Valley Civilization between 2600 and 1900 B.C., is the limited information the inscriptions reveal. Thousands of examples have been discovered across sites like Harappa and Mohenjo-daro, most of them carved into small stamp seals likely used in trade. The majority are extremely short, making it almost impossible to identify grammar or build meaning.

Archaeological context offers only partial help. The cities of the Indus Valley were repeatedly rebuilt, disrupting the original placement of artifacts. As a result, it’s difficult to connect inscriptions to specific activities or environments. That uncertainty has fueled a long-running debate over what the Indus script actually represents. Some scholars argue the symbols may not constitute a fully developed writing system at all, while others point to recurring structural patterns and similarities to those seen in other early civilizations as evidence that the script likely carried linguistic meaning.

For societies that existed or flourished during the same historical period, “people needed information technologies including writing,” explains Massimo Vidale, a professor of archaeology at the University of Padua in Italy. “In ancient Mesopotamia and India writing seems to be born in the context of economical-productive interactions," he says. However, Vidale cautions that researchers still cannot say with certainty that all Indus symbols carried the same meaning or function.

The wooden tablets containing the Rongorongo script were first documented in the 1860s by European missionaries on Easter Island, who encountered them among the Rapa Nui people. By that point, knowledge of how to read them had already been lost. Today, only a few dozen examples survive, scattered across museums and private collections.

Rongorongo presents researchers with several major obstacles. The surviving inscriptions are too limited in number and length to provide the kind of repeating patterns needed for decipherment. Scholars also lack clarity around the underlying language, though it is widely believed to be connected to Polynesian languages spoken across the region. Even the direction of the writing remained a mystery for years. Today, most experts believe the script follows a reverse boustrophedon pattern, meaning the text alternates direction from one line to the next.

Dating to around 3100 to 2900 B.C., Proto-Elamite is an early Bronze Age script that was used in what is now Iran. It appears primarily in administrative contexts, recording economic transactions and resource management. There are over 1,700 surviving tablets. The main challenge in understanding the script is its complexity. It contains roughly 1,200 signs, many of which vary subtly in form. Scholars still debate how many symbols the system actually includes, making it difficult to establish a solid framework for analysis.

Researchers have started to digitize and categorize the signs using artificial intelligence. “While computational approaches offer processing power above human capability, they rely heavily on the quality and consistency of the data," cautions Philippa Steele, a principal investigator of visual interactions in early writing systems at Magdalene College. "Problems with the data can seriously undermine the effort and lead to misleading results.”

Discovered in 1908 by Italian archaeologist Luigi Pernier during excavations at the Minoan palace of Phaistos, the Phaistos Disc is a one-of-a-kind artifact. The fired clay disc, roughly six inches across, is stamped on both sides with symbols arranged in a spiral pattern. In total, it contains 241 impressions made from 45 distinct signs.

Dating to the Minoan Bronze Age, the disc appears to contain a deliberate and structured system of symbols, yet no one knows exactly what that system represents. “With only one text… the nature of the corpus is an issue,” says Zender. There’s also no cultural context or clear indication of what the disc was used for.

“Unless things change radically, which can of course happen as archaeologists continue to discover new monuments and texts, or old manuscripts come to light, there's no hope for most of these [undeciphered ancient writing systems],” says Zender.