THE Incas left no doubt that theirs was a sophisticated, technologically savvy civilisation. At its height in the 15th century, it was the largest empire in the Americas. These were the people who built Machu Picchu, a royal estate perched in the clouds, and an extensive network of paved roads complete with suspension bridges crafted from woven grass. But the paradox of the Incas is that despite all this sophistication they never learned to write.

Or did they? The Incas may not have bequeathed any written records, but they did have colourful knotted cords. Each of these devices was called a khipu.

The Incan is one of few ancient civilizations that speaks to us in multiple dimensions. Instead of words or pictograms, the Incas used khipus—knotted string devices—to communicate extraordinarily complex mathematical and narrative information. But, after more than a century of study, we remain unable to fully crack the code of the khipus. The challenge rests not in a lack of artifacts, but in their variety and complexity. We confront tens of thousands of knots tied by different people, for different purposes, and in different regions of the empire.

Using locally available materials such as camelid fleece and cotton, the 'khipukamayuqs' (knot-makers/animators) encoded administrative data in the twisted strings of these ancient spreadsheets. The Inca bureaucrats used these data to keep tabs on the largest empire in the pre-Columbian Americas.

However, these quantitative khipus account for only about two-thirds of the samples remaining today. The remaining third of these devices, the so-called narrative khipus, appear to contain encoded nonnumerical, narrative information, including names, stories, and even ancient philosophies.

The search for a narrative “Rosetta khipu” amounts to finding a match between the text of a Spanish document and the knots of twisted strings. For those who love puzzles, the narrative khipus are a godsend.

They certainly went to great lengths to transport the khipus. Couriers would loop the cords over their shoulders and run with them across the empire. 

We thought the Incas couldn't write. These knots change everything. A lost language encoded in intricate cords is finally revealing its secrets, and it could upend what we know about Incan history and culture.