"There have been attempts to respond to the so-called Fermi Paradox (which, granted, is a paradox only if one accepts the optimistic parameters that most observers apply to the Drake equation). One common response is that a civilization may obliterate itself once it reaches radio capability. This explanation might be acceptable if we were talking about only a few such civilizations, but with the common SETI assumptions implying billions of them, it is not credible to believe that everyone of them destroyed itself."