The mystery surrounding a cryptic string-based communication system used by ancient Incan administrators may at last be unravelling, thanks to computer analysis of hundreds of different knotted bundles.
The discovery provides a tantalising glimpse of bureaucracy in the Andean empire and may, for the first time, also reveal an Incan word written in string.
Woven from cotton, llama or alpaca wool, the mysterious string bundles – known as Khipu – consist of a single strand from which dangle up to thousands of subsidiary strings, each featuring a bewildering array of knots. Of the 600 or so Khipu that have been found, most date from between 1400 AD and 1500 AD. However, a few are thought to be about 1000 years old.
Spanish colonial documents suggest that Khipu were in some way used to keep records and communicate messages. Yet how the cords were used to convey useful information has puzzled generations of experts.
Unpicking the knots
Now, anthropologist Gary Urton and mathematician Carrie Brezine at Harvard University, Massachusetts, US, think they may have begun unravelling the knotty code. The pair built a searchable database containing key information about Khipu strings, such as the number and position of subsidiary strings and the number and position of knots tied in them.
The pair then used this database to search for similarities between 21 Khipus discovered in 1956 at the key Incan administrative base of Puruchuco, near modern day Lima in Peru. Superficial similarities suggested that the Khipu could be connected but the database revealed a crucial mathematical bond – the data represented by subsidiary strands on some of Khipu could be combined to create the strands found on more complex ones.
This suggests the Khipu were used to collate information from different parts of the empire, which stretched for more than 5500 kilometres. Brezine used the mathematical software package Mathematica to scour the database for other mathematical links ? and found several.
“Local accountants would forward information on accomplished tasks upward through the hierarchy, with information at each successive level representing the summation of accounts from the levels below,” Urton says. “This communication was used to record the information deemed most important to the state, which often included accounting and other data related to censuses, finances and the military.”
And Urton and Brezine go a step further. Given that the Puruchuco strings may represent collations of data different regions, they suggest that a characteristic figure-of-eight knot found on all of the 21 Puruchuco strings may represent the place itself. If so, it would be the first word to ever be extracted from an Incan Khipu.
Completely deciphering the Khipu may never be possible, Urton says, but further analysis of the Khipu database might reveal other details of life. New archaeological discoveries could also throw up some more surprises, Urton told New Scientist.