Dinosaurs have roamed the earth and mastered the sky for over six hundred million years (give or take tens of millions). The various species carved out niches and lived either side by side in peace with each other or, in the case of the predators, roamed at will through their territories in search of prey. Having survived many close calls which would have devastated the dinosaur population, including what astrophysicists call several large "missed by just a whisker" asteroid strikes. The relentless nature of these noble creatures was unchecked until the most intelligent of mammals--Homo sapiens--came down from the trees and moved onto the plains.