The question that Inca scholars have grappled with since is whether or not the khipus constitute what linguists call a glottographic or "true writing" system. In true writing, a set of signs (for example, the letters C-A-T) matches the sound of speech (the spoken word "cat.") These signs must be easily decoded not just by the person who writes them, but by anyone who possesses the ability to read in that language. No such link has yet been found between a khipu and a single syllable of Quechua, the native language of the Peruvian Andes.
But what if the khipus don't fit neatly into the precise criteria established for true writing? It's possible, says Wisconsin's Salomon, that khipus were actually examples of semasiography, a system of representative symbols—such as numerals or musical notation—that conveys information but isn't tied to the speech sounds of a single language, in this instance Quechua. (By contrast, logographic languages such as Chinese and Japanese are phonetic as well as character-based.) The Incas conquered a huge number of neighboring peoples in a short time span, between 1438 and 1532; each of these groups had its own language or dialect, and the Incas wanted to integrate those new territories into their hyperefficient organizational network quickly. "It makes sense that they'd use a system that could transcend languages," Salomon says.
If khipus are examples of semasiography, the obvious next step is to break their code. Nearly a decade ago, Gary Urton, a professor of pre-Columbian studies at Harvard, began the Khipu Database project (KDB), a digitized repository of 520 khipus. (831 khipus are known to exist worldwide.) Urton has argued that khipus contain vastly more information than once believed—a rich trove of data encoded in each cord's colors, materials, and type of knot. The KDB may have already decoded the first word from a khipu—the name of a village, Puruchuco, which Urton believes was represented by a three-number sequence much like an Inca ZIP code. If he's correct, the system employed to encode information in the khipus is the only known example of a complex language recorded in a 3-D system. Khipus may turn out to be something like bar codes that could be "scanned" by anyone with the proper training.
The easiest way to know for certain if the khipus were a form of writing would be to find the Inca equivalent of the Rosetta Stone: a khipu paired with its written Spanish translation. Because of the limited number of khipus—only a fraction of the amount of material available to the researchers who decoded the Egyptian and Maya hieroglyphs—this has long been thought improbable. It's not impossible, though. A couple of decades ago, a 1568 real-estate document turned up in a Cusco archive that showed that Machu Picchu had once been a royal estate belonging to Pachacutec, the greatest Inca emperor. In the 1990s an Italian noblewoman claimed to have discovered a khipu with its translation among her family papers in Naples. Thus far, these controversial "Naples documents," initially a hot topic of speculation among historians, have turned out to be a dead end.
Then just last year, what may prove to be the most important evidence yet turned up in a tiny mountain village in Peru. Sabine Hyland, a professor of anthropology at St. Norbert College, found a "khipu board," a device Mercederian missionaries used to keep track of information such as attendance of natives at mass. The board, which dates from the 19th century, lists 282 names. Next to 177 of them is a hole with a corresponding khipu cord. While the board was created centuries after the Spanish conquest, its cords' various color patterns are similar to those found in khipus from the Inca period. Hyland has since located a second khipu board and plans to study both in depth later this year.
This is probably not an Inca Rosetta Stone. Hyland's early guess is that the strings don't represent the names exactly, but instead record mundane details like which residents of the village played a role in a holiday pageant or donated a sheep to the local fiesta. But if they do resemble 16th-century khipus as closely as she thinks they might, their decoding could at the very least be proof that the Incas used a semasiographic system. Such a breakthrough could begin to rewrite the narrative of a civilization whose history has been told almost entirely by the very conquerors who set out to erase it. It would also serve as a reminder to future researchers: Don't mistake your own lack of imagination for deficiencies in the cultures you study.
Also in Slate: Joshua Foer crosses the last remaining Incan grass bridge.