# Mathematical Digest

### Short Summaries of Articles about Mathematics in the Popular Press

"Cracking the Khipu Code," by Charles C. Mann. Science, 13 June 2003.

On the same topic:
"Researcher sees strands of ancient secrets," by Gareth Cook. The Boston Globe, 4 July 2003;
"Decoding The Secrets Of The Incas," by Drew Benson. Associated Press, CBSNews.com, 2 December 2003;
"Quipus could unlock mystery of Incas," The Washington Times, 9 December 2003;
"String Theory," by Eleanor Robson. American Scientist, March-April 2004.

The Science article---under the heading of "Anthropology"---is about decoding khipu (Incan knotted strings) and asserts that they are a form of written document. "Researchers take a fresh look at Incan knotted strings and suggest that they may have been a written language, one that used a binary code to store information," Mann writes. Although others have studied khipu, of which 600 survived the Spanish, no one has yet actually "translated" the encrypted strings into a narrative. Signs of the Inka Khipu, a new book by Gary Urton (University of Texas Press), attempts to unravel the mystery. He systematically broke down the elements of the khipu, created a database to identify patterns, and now proposes that khipu makers made use of the nature of spinning and weaving by assigning values to a series of binary choices, including the type of material (cotton or wool), the spin and ply direction of the string (which he describes as "S" or "Z" after the "slant" of the threads), the direction (recto or verso) of the knot attaching the pendant string to the primary, and the direction of slant of the main axis of each knot itself (S or Z). As a result, he says, each knot is a "seven-bit binary array," although the term is inexact because khipu had at a least 24 possble string colors. If Urton is right, khipu are "the world's sole intrinsically three-dimensional "written" documents."

--- Annette Emerson