That said, Reason magazine has a pretty interesting article up about the search for extraterrestrial intelligence Where are all the space aliens and do we really, really want to meet them?
Even if Sagan and Newman are correct that the galaxy is populated with saintly super-advanced intelligences, it is puzzling that no one has so far found any physically detectable astronomical evidence of their existences. Hanson also noted that our instruments should be able to detect some evidence for his postulated colonizing wave front as it progressed by converting matter and energy around various stars. There is, however, another possible explanation for this absence of evidence for extraterrestrial civilizations—intelligence could be toxic.
In 1996, Hanson formulated the idea that there is a Great Filter that somehow reduces the chances that a civilization can reach the stars before going extinct. The question then becomes is the Great Filter behind us or ahead of us? It might turn out that evolving life is highly improbable which would suggest that the Filter is behind us and that we are alone in the universe. Of course, finally detecting an alien civilization would be a positive event with regard to the Great Filter: if aliens have survived technological development, then so might we.
But what if we just find evidence of alien life? Oxford University transhumanist philosopher Nick Bostrom argues that finding fossils for independently evolved complex life on Mars would signal a dismal future for humanity [PDF]. “Such a discovery would be a crushing blow,” argues Bostrom. “It would be by far the worst news ever printed on a newspaper cover.” Why? Because it would mean that it is highly probable that life arises frequently in the universe.
In that case, since we have no evidence for extraterrestrial civilizations that would strongly imply that the Great Filter lies ahead of us, it is likely we will be winnowed out by it. Intelligent life might inevitably destroy itself by deploying apocalyptic technology, e.g., thermonuclear weapons, biotech plagues, runaway nanotechnology, or something else horrible that we’ve yet to imagine. Thus Bostrom concludes, “In the search for extraterrestrial life, no news is good news. It promises a potentially great future for humanity.” In other words, extraterrestrial silence is golden.