Do the reported discoveries of towering, human-like skeletons reveal that the world was once inhabited by giants? Historians and experts investigate various events, legends and texts throughout history that may contain evidence of contact between humans and extraterrestrial life. Ancient Aliens examines 75 million years of the most credible alien evidence here on Earth: from the age of the dinosaurs, to ancient Egypt, to the skies over the western desert in the present day US, ancient cave drawings of strange creatures, an asphalt-like substance in an Egyptian pyramid made from the remains of unidentified creatures, continued mass sightings in the USA.