While excavating an Inca outpost on Peru’s southern coast, archaeologist Alejandro Chu and his colleagues uncovered some twisted surprises.

In 2013, the scientists were digging in one of four rooms lining the entrance to what had been a massive storage structure, and they started finding sets of colored and knotted strings poking through the ground. Known as khipus, these odd Inca creations recorded census totals, astronomical events and other matters of state interest. In a society without a writing system, khipus also told stories about Inca rulers’ exploits.

That, at least, is what Spanish chroniclers wrote about khipus in the decades after toppling the Inca empire in 1532. But Spanish accounts, which were based on interviews with royal Inca record keepers, provide only general descriptions of these cord contraptions. Researchers have yet to decipher khipus from various parts of the Inca empire, and it’s a mystery what any particular cord array meant to its makers.

But Urton and Chu’s conclusion, while exciting, is only one small piece of a much larger puzzle. Approximately 1,000 previously discovered khipus exist, held in museums and private collections around the world. While those tens of thousands of knots are receiving increasing research scrutiny, most khipus remain frustratingly mysterious. To enable large-scale research, Urton and his colleagues have assembled detailed information about these khipus into a digital database, which investigators from Lima to London can consult in efforts to untangle the code — or codes — of the Incas’ cords.  

Knotty taxes

Research on how numbers were recorded on khipus goes back nearly a century. A series of thin, twisted cords arranged in tiers typically hang from one or more thick, horizontal cords. Knots in the bottom tier record 1s, knots in the next highest level record 10s and successively higher levels record greater powers of 10 (100s, 1,000s and so on).

Inkawasi khipus express a code of their own, unlike anything seen on knotted textiles from other Inca sites, Urton and Chu conclude. Storehouse cords excavated by Chu’s team contain what amount to simple numerical equations, represented as a = b c, with any of four fixed values assigned to b.

khipus bag

Still, even deciphering, say, a pre-conquest khipu’s tale of an Inca king’s exploits might leave scientists confused. There is no reason to expect that the Inca regarded history as a linear series of events, with certain actions having specific consequences, Urton says.

A peculiarity of the night skies might have inspired an unusual Inca world view, he suggests. As the only ancient civilization located below the equator, in the Southern Hemisphere, the Inca neither saw nor probably imagined the existence of a North Star forever stuck in the same heavenly spot. Perhaps members of an ancient society untethered to a secure cosmic landmark thought in ways that people today can’t begin to grasp, Urton speculates. “Every point in the Inca universe was in motion.”

But even the Inca, it seems, couldn’t move fast enough to dodge taxes.


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