Original: Social concerns Sagan believed that the Drake equation , on substitution of reasonable guesstimates , suggested that a large number of extraterrestrial civilizations would form , but that the lack of evidence of such civilizations highlighted by the Fermi paradox suggests technological civilizations tend to destroy themselves rather quickly .
Simplified: Social concerns Sagan also believed that the Drake equation suggested that many kinds of intelligent life could form , but that the lack of evidence ( the Fermi paradox ) suggests that intelligent beings destroy themselves rather quickly .