and i saw somewhere that dinosaurs became extinct due to smoking, not a meteor ...
Dinossaurs learned how to use artifacts, then weapons, rockets and so on. They either fought each other to extinction or flew away from the planet leaving none behind.
Their bones and artifacts were never found because they stayed here for relatively short time span (a few hundred thousand years) many millions of years ago.
Life repeats itself...
(Not my idea, but can't remember the author's name)
