The earliest records of the Inca in South America date back to the 12th century. Over the next 300 years, the Inca of Cuzco, Peru, expanded their empire by conquering nearby communities. In the century before the Spanish Conquest, the Inca Empire spanned South America from Chile to Colombia.
Knot for Everyone
The Inca kept records using a mathematical system of knots called a quipu. Using a base 10 system, they knotted strings to represent place values, similar to the numbers we use today. Strings of contrasting colors represented the objects being counted. Wherever a quipu went, a trained expert followed, in order to translate its information and maintain its accuracy.
In addition to the quipu, the Inca used a counting board, similar to an abacus, called a yupana. Sometimes yupana could be as big as a table. Unfortunately, there is not as much information about how to use this tool.
The Inca were expert architects and engineers even without the use of wheels, draft animals or iron tools. In a short period of time, the Inca created a sophisticated network of roads and structures. Many of these structures are still perfectly intact today.
Ancient Inca construction was so precise that stone buildings were built without the use of mortar. It is said that their stones fit together so perfectly that a knife blade could not fit between them. This expert interlocking arrangement provided enough flexibility that during earthquakes the walls were able to wobble. Once the tremors ended, the stones settled back into place. Reports abound in Peru of earthquakes leveling modern buildings while centuries-old Incan walls stayed put.