WASHINGTON, Sept. 16 (UPI) -- A handful of 6,200-year-old cloths recovered an archaeological site on the coast of Peru offer the earliest evidence of the use indigo as dye. The indigo-dyed fabrics predate similar Egyptian artifacts by at least 1,500 years.
The cloths were first unearthed from Huaca Prieta, an ancient ceremonial mound in northern Peru, in 2007, but the fabrics' age and the presence of indigo were only recently confirmed.
"It is possible it is the earliest known example of cloth dyeing in the world," Jeffrey Splitstoser, an anthropologist at George Washington University, told the Los Angeles Times. "I don't know of anything older."
The cloth pieces are just a few of several hundred scraps of fabric recovered from the site of the ancient mound and temple. Splitstoser has examined at least 800 of them.
The significance of the pieces described in the journal Science Advances wasn't initially apparent.
"They were literally sealed under these new layers of building, but because the building material had so much ash in it, it leached into the textiles, making them a very dirty, sooty color," Splitstoser told Live Science.
After a careful washing, the faded blue indigo stripes were revealed.
A chemical analysis technique called liquid chromatography, designed to isolate parts of a mixture, revealed the presence of indigo in five out of eight tested fabrics.
Researchers say the ancient peoples of coastal Peru likely sourced the dye from the plant Indigofera. Indigo was one of antiquity's first and most valuable dyes, and the ancient people of South America were apparently leading the way in its use.
"The people of the Americas were making scientific and technological contributions as early and in this case even earlier than people were in other parts of the world," Splitstoser told Live Science. "We always leave them out. I think this finding just shows that that's a mistake."