How it began
A quipu, also spelled khipu, is a record made of knotted cords. The word means 'knot' in Quechua. Objects that can be clearly identified as quipus first appear in the archaeological record of the central Andes in the 1st millennium CE and are likely the work of the Wari. The Inca later developed the device into the main record-keeping tool of their empire, which lasted from about 1400 to 1532 CE.
How it works
Quipus are made of spun and twisted cotton or camelid fiber such as llama or alpaca. Knotted pendant cords hang from a main, or primary, cord. On Inca quipus, numbers are stored in a decimal positional system: knots are grouped by position along the cord to mark ones, tens, hundreds and so on, and the absence of a knot in a position stands for zero. Different knot types are used, including single knots and long knots with several turns. Cord color is thought to encode categories.
The quipu was for keeping records, not for calculating. Counts such as the number of people in a community or the amount of food harvested were stored on it. Some older Wari quipus appear to use base 5.
What lasted
The quipu let the Inca state store census, tribute and other data without a written script, and UNESCO describes surviving quipus as the only record we possess of the empire made by the Inca themselves. Cord records continued in use in the Andes through the colonial and republican periods in changed forms.
Modern study began with Leland Locke, a mathematics teacher who examined quipus at the American Museum of Natural History and published in 1912. He showed that top cords held the sums of the cords beside them, which proved the decimal system. That numerical reading remains the only undisputed decipherment. Whether quipus also recorded narrative is still debated.
Where it stands today
A total of 923 quipus have been inventoried in 88 museums in South America, North America and Europe. Because the cords are brittle, the record of what they contain matters as much as the objects. Marcia and Robert Ascher began recording quipus in a standard format in the 1960s. In 2002 Gary Urton started the Harvard Khipu Database, which holds electronic records of 544 quipus and was entered on UNESCO's Memory of the World regional register for Latin America and the Caribbean in 2016. Researchers now run statistical analyses across open databases of more than 600 quipus.
