Long ago, in a galaxy that is our very own, lies the same solar system that we grew up in, only at an earlier date. The difference was that the pre-human solar system had a planet that was situated between Mars and Jupiter, whereas today, it is the location of a dispersed asteroid belt. So, what happened? First off, planet 4A was like the other inner planets: rocky. Beyond those, existed the next 4 planets which were gas giants with no solid surface to stand on. That made it difficult to walk, so they were critterless. Early life originated on Venus billions of years ago and, through the ignorance of the creatures inhabiting that planet, methane gases eventually decimated life there, so off to Earth they went. Chemical rockets that man invented for his interplanetary travel were never utilized by ancient life. After billions of years of knowledge, they elected to pursue gravitational waves for creature transportation. After materializing on Earth, they evolved into dinosaurs who reigned from 220 to 65 million years ago. This 155-million-year era saw much advancement in science. The waves were utilized to take the dinosaurs from here to Mars and 4A, to experience different environments for their intellectual pleasure. All was good. Then one day, 65 million years ago, an inept dinosaur, named Barney, started messing with the gravitational waves and created a rift in the space/time fabric. This caused planet 4A to disassemble because gravity could no longer hold the planet into the sphere it once was. It dispersed into the asteroid belt we see today. The transportation link to Mars broke down and blew its atmosphere out into space. The resulting repercussion on Earth was that all land walking dinosaurs were catapulted into the sky. When the gravitational waves suddenly subsided, all the walking dinosaurs fell to their death. The flying versions survived and became our birds. Bonehead Barney caused massive extinction and decimated 4A. Bad Barney.