Original: In the end, the narrator says that humans would never have existed if a chance collision in space 165 million years ago had n't occurred, sending an asteroid hurtling towards Earth and dooming the dinosaurs to extinction.
Simplified: In the end, the narrator says that humans would never have existed if a chance collision in space 150 million years ago had n't occurred, sending an asteroid hurtling towards Earth and dooming the dinosaurs to extinction.