History of life on Mars and beyond

The theory am looking at, is that if the asteroid belt, is in fact a planet which was destroyed, could not that have had a catastrophic event on Mars, forcing the life on Mars if existed to seek another world such as Earth. It would be interesting know if this event did take place, and when. If possibly you could correlate the event to match with the extinction of the dinosaurs and then the emergence of man on Earth. So what I am proposing is that if the 3 events took place, and at the appropriate time, then the theory could hold. Don't know how you can go about proving this. But it sounds logical. Any Thoughts....