DENVER, COLORADO—Western Digs reports that Durham University archaeochemist Denise Regan has discovered traces of salicylic acid, a precursor compound of aspirin, on an unassuming, 1,300-year-old ceramic sherd unearthed in a rock shelter in eastern Colorado. The discovery could be the earliest proven use of the chemical in North America, and offers a unique glimpse at prehistoric medicinal practices. Derived from willow bark, salicylic acid is still used by some Native groups today to cure aches. “If you talk to the Arapahoe or the Cheyenne, they’ll use willow bark either as a tea with the leaves or they will soften the bark in boiling water and chew on it for toothaches and as a pain reliever,” says Regan. She believes the sherd itself could have come from a vessel that was reserved for preparing poultices or tea. "I think it’s reasonable to infer that this pot was used for medicinal purposes and not to cook food. If it was used to cook food we would’ve more than likely found something else in there.”