Our belief structure highly influences our explanation and conclusions concerning ambiguous stimuli. When it was accepted by most Westerners that humans and all life were direct creations by God, if other worlds existed and had life, it must have also been created by God. Acceptance of non-theistic evolution indicated that if life evolved on earth, it could likewise have evolved elsewhere. This life could be either a "lower" or "higher" level than humankind, or an entirely different kind based on a non carbon molecule. If many kinds and types of life exist elsewhere in the universe, their visits to earth become a real possibility. Today, some exobiologists such as Carl Sagan and others have postulated that it is highly probable that life exists in many far off places in the universe. This paper hypothesizes a relationship between public belief in evolution and the number of claimed sightings of UFOs. Before the late 1940s, there were almost no reports of UFOs. The acceptance of evolution, the first famous claimed sighting in 1947, the American space program, and the fear of invasion from foreign powers with advanced technology (especially the former Soviet Union) have all contributed to the phenomenal number of claimed UFO sightings since 1947.