Do you think its possible that a race of humans existed before the dinosaurs roamed the Earth?

Some people have theorized that a human race could have existed before the dinosaurs. There has been a couple of things that have been found that pre date any known human existance on this planet. One for instance was a set of footprints that appear to be wearing shoes that was frozen in time in a substance (I forgot the substance) and the date they were made long, long pre dated our current human existance on this planet. If this is possible, and the human race was just as advanced as we are today, is there anything they could have left to prove there existance over 500 million years later. If our civilazation ended today I can think of nothing that would exist 500 million years from now, can you?