Aliens and the Buried Past

Archaeologists have uncovered temple complexes dating far back into human prehistory. They've identified ancient constructions submerged deep in our oceans, and even discovered that many of today's sacred sites were constructed atop older ruins. Does the mounting evidence suggest the presence of an advanced civilization lost to time? And, as Ancient Astronaut theorists propose, might these structures belong to an extraterrestrial epoch in Earth's history?