When the Yale University history lecturer Hiram Bingham III encountered the ruins of Machu Picchu in Peru 100 years ago, on July 24, 1911, archaeologists and explorers around the world (including Bingham himself) were stunned, having never come across a written reference to the imperial stone city. Of course, the absence of such historical records was in itself no great surprise. The Inca, a technologically sophisticated culture that assembled the largest empire in the Western Hemisphere, have long been considered the only major Bronze Age civilization that failed to develop a system of writing—a puzzling shortcoming that nowadays is called the "Inca Paradox."
The Incas never developed the arch, either—another common hallmark of civilization—yet the temples of Machu Picchu, built on a rainy mountain ridge atop two fault lines, still stand after more than 500 years while the nearby city of Cusco has been leveled twice by earthquakes. The Inca equivalent of the arch was a trapezoidal shape tailored to meet the engineering needs of their seismically unstable homeland. Likewise, the Incas developed a unique way to record information, a system of knotted cords called khipus (sometimes spelled quipus). In recent years, the question of whether these khipus were actually a method of three-dimensional writing that met the Incas' specific needs has become one of the great unsolved mysteries of the Andes.
No one disputes that the Incas were great collectors of information. When a battalion of Spanish conquistadors, led by the ruthless Francisco Pizarro, arrived in 1532, the invaders were awed by the Inca state's organization. Years' worth of food and textiles were carefully stockpiled in storehouses. To keep track of all this stuff, the empire employed khipucamayocs, a specially trained caste of khipu readers. The great 16th-century Spanish chronicler Pedro Cieza de León recalled that these men were so skilled that "not even a pair of sandals" escaped their annual tallies. The Spaniards, who were no slouches themselves in the bureaucracy department—Pizarro's landing party included 12 notaries—observed that the Incas were remarkably skilled with numbers. For many years during the 16th century, says Frank Salomon, a professor of anthropology at the University of Wisconsin, Inca khipucamayocs and Spanish accountants would square off in court during lawsuits, with the khipu numbers usually deemed more accurate.
Individual khipus seem to have varied widely in color and complexity; most of the surviving examples generally consist of a pencil-thick primary cord, from which hang multiple "pendant" cords. From those pendants hang ancillary cords called "subsidiaries." One khipu has more than a thousand subsidiary cords. Sixteenth-century eyewitness accounts describe khipucamayocs studying their khipus intensely to access whatever details had been recorded on them. According to Spanish chronicles of the 1560s and 1570s, some khipus appeared to contain information of the sort that other cultures have typically preserved in writing, such as genealogies and songs that praised the king. One Jesuit missionary told of a woman who brought him a khipu on which she had "written a confession of her whole life."
The Spaniards' institutional response to this singular accounting system, originally benign, shifted in 1583, when Peru's nascent Roman Catholic church decreed that khipus were the devil's work and ordered the destruction of every khipu in the former Inca empire. (This was the heyday of the Spanish Inquisition, and the church was making a major push to convert natives from their pantheistic state religion.) By the middle of the 17th century, Spanish accounts, the only historical sources available from that time, began to cast doubt on the idea that the khipus had ever been "read" like texts. Instead, the knots on khipus came to be viewed as mnemonic prompts analogous to the beads on Catholic rosaries, cues that supposedly had helped the khipucamayocs recall information that they had already memorized. Some scholars argued that a khipu could have only been understood by the same khipucamayoc who'd made it. Andean cultures secretly continued to use knotted cords to record information well into the 20th century, but the links between modern cords and Inca khipus aren't clear. What's certain is that no one in recent history has been able to fully interpret an Inca khipu.
The conquerors' mnemonic theory held sway for three centuries, and was buttressed in 1923, when the anthropologist L. Leland Locke analyzed 42 khipus at the American Museum of Natural History in New York City. Locke demonstrated how the knots represented the results of tabulations. These figures were grounded in the base-10 decimal system (tens, hundreds, thousands), and so were analogous to the beads on an abacus. Despite the evidence from 16th-century eyewitness accounts, the academic community accepted the hypothesis that the Inca, who had built the world's largest highway system and eradicated hunger in an empire of more than 10 million people, never managed to express their thoughts in written form.
In 1981, however, the husband-and-wife, archeologist-and-mathematician team of Robert and Marcia Ascher put the Inca Paradox into doubt. By closely analyzing the position, size, and color of the knots in 200 khipus, they demonstrated that about 20 percent of them showed "non-arithmetical" properties. These cords, the Aschers argued, seemed to have been encoded with numbers that might also represent other information—possibly some form of narrative.
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.