“What if technological species pop up all the time, in all appropriate locations, everywhere in the universe, and when they do evolve, they change the conditions of their own planet so drastically that they obliterate themselves and perhaps all life on that planet within a century or two, leaving little or no trace of their own existence, beyond the fossilised rubble they created and then destroyed? The notion that humans could in some way destroy the living conditions that encouraged the evolution of a contemplative and curious bipedal mammal with a gift for malevolence, metalwork and ballistic missiles has been around for a long time.”