The Outer Space Connection (1975)

Speaking of the ambience of the 70s, surely nobody was as perfectly endowed to narrate an Ancient Astronaut documentary as the late, great Rod Sterling, who sadly died the same year that The Space Connection was released.  It was the precursor to the In Search Of...series, in which television astronaut and Tolkien scholar Leonard Nimoy took over as narrator from Sterling.  They don't make these things like they used to - the more recent Ancient Aliens series on the History Channel rehashed much of the same material with all the otherworldly atmosphere of a late night infomercial for exercise equipment.