Overview: Three ancient artifacts that could turn the history of the world upside down: In a Mexican cave, a young girl finds a bizarrely-shaped thousand-year-old skull that may prove aliens once walked the planet; featuring detailed images of dinosaurs, a Peruvian doctor discovers ancient stone carvings that could rewrite the story of evolution; and, excavated from one of Cairo’s oldest pyramids, a 2000-year-old wooden model may be proof that ancient Egyptians invented modern flight.