Quipu (Khipu), Inca, AD 1430-1530 - A Collective Memory: The only form of writing known in pre-Columbian South America, Quipu are still one of the great mysteries of archaeology as they have never been deciphered. These Quipu have been found at late Chachapoya sites and reflect the essential role of trade in this society. The different colours, twining, knot styles and lengths of string all hold information that can be read by a Quipu reader, knowledge that might have been lost to us forever.
The traditional Inca quipus were numbers expressed by knots on a section of rope. Unlike the Arabic numbers which uses ten different symbols for each digit (0 to 9), quipu makers tied multiple knots in a tight sequence represent a "digit". Digits can range from no knots (empty space) representing zero, to nine knots representing nine. Seven knots in a sequence equals the digit 7. A quipu could have only a few or up to 2,000 cords.