If an asteroid hadn't collided with the Earth 65 million years ago we would not be here today. Reptiles would still probably rule the world and apes would never have evolved. There was so much devastation after the impact that only small animals survived - very small mammals. These small creatures only came out into the open to take over the world when it was safe after the dinosaurs had gone. Mankind's development actually depended on the dinosaurs existence. Small animals evolved to give birth to live young so dinosaurs could not eat their eggs. Even giving milk to their young was to avoid the danger from dinosaurs. Becoming warm blooded allowed them to hunt at night which dinosaurs could not do. After the dust had settle it was a virtual paradise for mammals. The sun came out and they basked in it. A niche for large animals was vacant so mammals grew large and were successful. The climate changed and trees disappeared. Large mammals grazed happily until an intelligent a...