HAFR AL-BATIN, SAUDI ARABIA—Textile archaeologists have unearthed a section of coarsely woven Sumerian goat's wool bearing what could be the world's oldest, and perhaps its toughest, stain. "The stain, in scientific terms, is 'ground-in,' doubtless one of the active-lifestyle stains that plagued Sumerian families," said Leigh Perkins, the leader of the Tulane University team that uncovered the stain. "We hope to determine whether it's mud, blood, or some kind of blueberry proto-pie." Scientists say they can learn a lot from the discovery, such as how tough the Sumerians were on grime.