4 Ancient Civilizations That Mysteriously Crumbled — and Have Scientists Puzzled
History is full of mysterious disappearances — of people, of places and even of entire civilizations. In many cases, time has not told us what happened to the populations that have vanished en masse, all over the world. Archeologists unearth ruins and uncover clues as to the demise of ancient cultures, but the fates of many inexplicably evaporated peoples remain question marks. Here are four mysteriously vanished civilizations that keep scientists scratching their heads.