How the Quipu (Khipu) Recording System Worked
The quipu (also khipu, from the Quechua word khipu, meaning “knot” or “to knot”) was a knotted-string device used for record keeping in the Inca Empire. A quipu consisted of a primary cord, from which hung a series of pendant cords, each of which carried subsidiary cords. The pendant cords were marked with knots tied at specific positions, and the knots were combined in a system of positional notation to record numbers. The color of the cords, the direction of the knot twists, and the arrangement of the subsidiary cords encoded additional categories of information, including the type of record, the subject, and the source. The system was used for census data, tribute lists, military rosters, storehouse inventories, and (as recent research has shown) possibly for historical narratives, calendrical information, and even sacred or literary content.
Physical Construction
The physical structure of a quipu was both simple and elegant. The principal element was the primary cord (urku in some reconstructions), a horizontal cord from which the rest of the quipu was suspended. From the primary cord hung a series of pendant cords (hualu or similar terms), which were the main carriers of information. The pendant cords were, in turn, attached to a series of subsidiary cords (chiqan), which were smaller cords that branched off the pendants and which carried subsidiary or related information. The number of pendant cords on a quipu could range from a few dozen to several hundred, and the total length of the quipu could range from a few centimeters to several meters.
The cords of a quipu were made from the wool of llamas, alpacas, or sheep, spun and twisted in a variety of ways. The Spanish chronicler Garcilaso de la Vega recorded that the cords were made from llama wool and that the colors were chosen to indicate the type of record: white for silver, yellow for gold, red for the army, green for maize, and so on. Modern studies of surviving quipus have confirmed that the colors were used systematically to encode categorical information.
Knot Notation
The numerical information on a quipu was encoded in the knots tied on the pendant cords. The system of knot notation was a positional decimal system, similar in principle to the Arabic numerals now in use worldwide. Each pendant cord carried knots in a vertical column, and the position of a knot in the column indicated its place value. Knots at the bottom of the cord represented the units (1-9), knots in the middle represented the tens (10-90), and knots near the top represented the hundreds (100-900) and thousands (1000+). The position of the knots was determined by the convention that the highest place value was at the top of the cord and the lowest at the bottom, and the knots were separated by a fixed interval of empty cord.
The knots themselves were tied in three principal types:
- Simple (overhand) knots (chimpu in some sources), the most common type, used to represent the values 1-9 in a given position. A series of simple knots, tied side by side, indicated the number of units: two simple knots, for example, indicated the value 2 in that decimal position.
- Long knots, a single overhand knot with one or more turns of the cord wrapped above the knot; the number of turns indicated the value (typically 2-9), allowing a value of 2 through 9 to be recorded in a single knot without repetition.
- Figure-of-eight knots, in which the cord was tied in a figure-of-eight pattern; these were typically used to mark the value 1 in the higher decimal positions (tens, hundreds, thousands).
The combination of these knot types in a vertical column allowed the recording of any number, however large, with a high degree of accuracy. The Spanish chronicler Pedro Cieza de León reported that the quipucamayocs could record and retrieve information with great speed and accuracy, and that the system was so well developed that the imperial state could keep track of the population, the tribute, and the military resources of the entire empire.
Encoding of Categorical Information
In addition to the numerical information encoded in the knots, the quipu encoded categorical information in several ways. The most important was the color of the cords. The Spanish chroniclers record that the colors of the quipu cords were chosen systematically to indicate the type of record: white for silver, yellow for gold, red for the army, green for maize, black for time, and so on. The use of color allowed the quipucamayoq to identify the content of a quipu at a glance, without having to read the knots, and it was particularly useful in the storage and retrieval of quipus in the state archive.
Other categorical information was encoded in the direction of the knot twists and in the direction in which the subsidiary cords branched off the pendants. Recent research, particularly the work of Gary Urton and Sabine Hyland, has shown that the direction of the knot twists and the orientation of the subsidiary cords encoded additional layers of information, including the source of the record, the location of the people or goods being recorded, and (in some cases) the identity of the people involved. The system was, in effect, a complex semiotic system in which the same quipu encoded multiple overlapping categories of information.
The arrangement of the pendant cords on the primary cord also encoded categorical information. In some quipus, the pendants were arranged in a single row, and the order of the pendants indicated the order of the records. In other quipus, the pendants were arranged in groups, with each group corresponding to a particular category of record.
The Quipucamayocs
The quipucamayocs (keepers of the quipus) were a distinct class of officials who served at the court of the Sapa Inca, in the regional capitals, and in the provinces. They were trained from youth in the interpretation of quipus, and they were responsible for recording the affairs of the empire. The chronicler Garcilaso de la Vega recorded that the quipucamayocs were organized in a hierarchy parallel to the administrative hierarchy: there were quipucamayocs for each household unit, each district, each province, and the empire as a whole, and each level reported to the next. The death of the Sapa Inca or the appointment of a new governor was often accompanied by the rebinding of the quipus, a ceremonial act of administrative accounting that signaled the transfer of authority.
The post-conquest persecution of the quipucamayocs by the Spanish administration, which saw the quipu system as a form of idolatry and a barrier to the introduction of European record-keeping, led to the gradual loss of expertise in the interpretation of quipus, and the system fell into disuse in the late sixteenth and seventeenth centuries.
Historical Significance
The quipu was the principal technology of administration of the Inca state, and it allowed the imperial bureaucracy to keep detailed records of population, tribute, and military resources across a population of perhaps 12 million people. The system was, in effect, a form of writing in a broad sense, in which the knots and cords encoded multiple overlapping categories of information. The interpretation of quipus has been a major problem in Andean studies, but recent research has made substantial progress, and the decipherment of the quipus is now an active and productive area of research. The quipu is recognized as one of the most distinctive and sophisticated technologies of the pre-industrial world.