After analyzing a submerged bridge found in a Spanish cave, researchers have determined that humans inhabited the area earlier than previously thought.A submerged, human-constructed limestone bridge found inside a cave on a Spanish island is much older than previously thought, pushing back the record of when humans inhabited the location, a new study finds.Researchers discovered the limestone bridge in 2000 during a scuba-diving expedition inside the flooded cave in Mallorca, a Mediterranean island located off the eastern shore of Spain's mainland. At the time, researchers determined that the 25-foot-long (7.6 meters) bridge, which consists of large limestone blocks stacked on...