Ancient Astronaut Theorists discover evidence of a writing system that would radically alter the timeline of human history, in this clip from Season 15, "The World Before Time." Watch all new episodes of Ancient Aliens, Fridays at 8/7c, and next day on The HISTORY Channel website at ...

Ancient Astronaut Theorists believe that past evidence of ancient civilizations may have been destroyed. See more in this clip from Season 15, "The World Before Time." Watch all new episodes of Ancient Aliens, Fridays at 8/7c, and next day on The HISTORY Channel website at ...