Oldest Traces of Indigo Blue Found in Peru

Indigo blue is that special shade of blue that lends its color to our blue jeans. Used by many civilizations, from China to Egypt to South Africa, indigo used to be one of the most precious dyes of the ancient world. The oldest findings related to indigo blue so far dated back to 4400 years ago, and came from ancient Egypt. The latest findings have drawn back the date by about 1500 years, and have pointed to Peru as the place where humans first learned to dye fabric in this unique color.

Cloth pieces unearthed in Huaca Prieta in northern Peru have been so well preserved thanks to the dry climate of the region that the indigo dye on them is still recognizable. It is impossible for cotton cloth to survive intact for 6000 years in most places and climates around the world.

In the Andes region, which Peru is part of, the use of domesticated cotton (Gossypium barbadense) dates back to 7800 years ago. Radiocarbon dating has concluded that the cloth pieces found in Huaca Prieta are 6200 to 6000 years old, making them the oldest known examples of indigo painted cotton cloth. New research published in the Science Advances journal also includes data related to the indigotin and indurbin fund on the cloth, the main chemical compounds that form indigo blue. It is believed that indigotin has been extracted from a certain species of indigo tree native to South America.