When I was a kid, there was an older guy who frequented our local McDonald's and always carried around a box full of random papers and a fly swatter. He was an archetype of the UFO enthusiast — sort of a kook but a lot of fun to talk to.

In the 1990s, there was something of an alien abduction craze that swept the country. The popular show Unsolved Mysteries featured them, and an entire TV series, The X-Files, was built around the belief that extraterrestrial life had taken a keen (and perhaps malevolent) interest in Earth. (Of course, the aliens were also working in collaboration with the U.S. federal government.)

However, outside of popular culture, few serious intellectuals took the notion of aliens seriously. It certainly was not a major academic topic. The prevailing view was that life is uncommon throughout the universe, and Earth just might be the only planet lucky enough to have it.\

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