There would still be enough of these elements to form planetary systems after only a few billion years. In principle, the first intelligent life could probably have developed within 5-10 billion years of the Big Bang. In any event, a billion plus year headstart is a billion plus year headstart: the advances that existing for almost the order of a million times longer than our civlization must provide would be mind-boggling.
Originally posted by RobS
Any other civilisations out there won't have had a 15 billion year head start on us. They'd also need to wait for a whole generation of stars to form and supernovae in order to provide enough variety of heavy atoms to allow complex life, I doubt that you can get very far along the life\evolutuionary paths with just Hydrogen, Helium and Lithium.
A miniature black hole would accomplish the job in much more spectacular fashion.
Destroying us from space wouldn't be prohibitely costly, it would take one big rock, carefully steered to hit our planet, if they were good enough the moon could be used, although that does require them to get rather close, best to pick one of the huge slow ones in the asteroid belt, attach some engines, write your c code to provide the control mechanism to make it hit us, no more people.