The Inca had a mighty civilization. They built an empire that was the largest in the Americas before the arrival of the Spanish. It extended all the way along the west coast of South America from Bolivia to Chile.

The Inca created a 25,000-mile mountain highway system complete with rope bridges. They planted millions of acres of terraced farmland high in the mountains and constructed a temple on top of a 1.5-mile-high peak. They even figured out how to freeze-dry potatoes.

Yet, the Inca never developed a system of writing. What they did have were called khipu. These were knotted lengths of string made from cotton, llama wool or alpaca wool. The khipu hung in rows like a curtain from a thicker central rope. The bundles of string were often color-coded, although the colors have faded on most surviving khipu. Today, most are a similar golden brown. Bundles could contain just a few strings or hundreds of strings.

Few Khipu Survived The Spanish Invasion
When the Spanish conquistadors arrived and wiped out the entire Inca civilization, they found khipu everywhere. Unfortunately, the Spaniards destroyed many of them. They believed the knotted colored strings were meaningless.

In the 1920s, a science historian named Leslie Leland Locke discovered that the knots in a khipu represented numbers. He realized the bundles were record-keeping devices. He suggested they could have been used for several different purposes. For example, they were probably used to count and record information about the local population. They could also have been used to record the contents of storehouses.

Locke also figured out how the system worked. The height of a knot and its position on its string represented units — tens, hundreds, thousands and so on. The position of a string off the main rope represented things like specific people or villages. However, some of the khipu did not fit that pattern. Locke figured these were used for ceremonial purposes.

The Khipu Held The Empire's History
There is some evidence khipu were used for much more than just record-keeping. They might have been able to give complete accounts of events. For example, one 17th-century Spanish conquistador reported meeting an Inca man who carried khipu with him. The man insisted his khipu told of all the deeds of the Spanish in Peru, good and bad.

Perhaps khipu really were used for such purposes. However, it has been nearly impossible to find living people who can help to reveal the secrets of the knots.

Some new clues have emerged, however. Since the early 1990s, a professor named Gary Urton has been working to figure out what those khipu that were not used for record-keeping might mean. Urton is an anthropologist, a scientist who studies human culture and society. He has discovered that the position and height of the knots are not the only important things to look at when reading a khipu.

Also important are the color of the string, the direction the knots are twisted and the type of knots used. Urton has recently shown that the direction in which the knots are tied could show what clan a person belonged to. A clan is a group of people who are related in some way. It can be based on family connections. It can also be a group of people with the same job or skill.

Some Villagers Have Shared Khipu Knowledge
Recently, Scottish researcher Sabine Hyland discovered that some small villages in the Andes Mountains still have khipu. Since then, the villagers have shared some new information.

For example, they have explained that the materials used in the strings are important. Different materials have different meanings. The villagers said khipu were used to tell different kinds of stories. They were used to give accounts of warfare. Hyland has even found evidence of phonetic symbols in the strings. Phonetic symbols represent spoken sounds.

The Incas might have failed to develop a way to represent words with symbols. Or maybe we have been underestimating them
. Perhaps they had their own very special way of telling stories. We might be closer to finding that out.

Which sentence from the article supports a main idea of the article?
A. The khipu hung in rows like a curtain from a thicker central rope.
B. The bundles of string were often color-coded, although the colors have faded on most surviving khipu
C. When the Spanish conquistadors arrived and wiped out the entire Inca civilization, they found khipu everywhere.
D. The villagers said khipu were used to tell different kinds of stories.