The Marsoulas conch hasn't been heard since the late Stone Age.The sound of the Marsoulas conch hasn't been heard for 18,000 years. At the entrance to the Marsoulas cave in France's Pyrenean foothills, Henri Begouën and James Townsend Russell stumbled upon an exceptional find in 1931. A conch shell -- the hardened exoskeleton of a predatory sea snail -- lay empty at the mouth of a cave the men knew was once used by human ancestors in the late Stone Age. But, as exceptional as the find was, the researchers filed the conch away, believing it to have no sign...