A large conch shell overlooked in a museum for decades is now thought to be the oldest known seashell instrument — and it still works, producing a deep, plaintive bleat, like a foghorn from the distant past. The shell was found during the 1931 excavation of a cave with prehistoric wall paintings in the French Pyrenees and assumed to be a ceremonial drinking cup. Archaeologists from the University of Toulouse recently took a fresh look and...