With the force of 10 billion atomic bombs, an asteroid struck the Earth 66 million years ago, altering the trajectory of evolution. As the sky grew darker, photosynthesis in plants also ceased. Then the animals that consumed the plants perished. The food chain disintegrated. All species disappeared, over 90% of them. Except for a small number of birds, all dinosaurs were extinct when the dust settled.
However, this terrible incident paved the way for human growth. The remaining mammals thrived, including the tiny proto-primate creatures that would eventually give rise to us.
Imagine the dinosaurs were still alive if the asteroid had missed. Imagine a group of highly advanced raptors setting up camp on the moon. Scientists studying dinosaurs might be learning about relativity or speculating about a scenario in which, amazingly, mammals colonised the planet.
Although it may sound like awful science fiction, this raises some important, philosophical issues regarding evolution. Is it really a coincidence that we have evolved into clever tool users, or is it a given?
35 million years ago, monkeys just continued to evolve and create new species of monkey. And at least three times, 55 million years ago, 50 million years ago, and 20 million years ago, primates made it to North America. They did not, however, develop into a species that produces nuclear weapons and smartphones. Instead, they became extinct for unknown reasons.