The Creation Evidence Musseum in Texas appears to have roof that man and dinosaurs existed together pre-flood. The have found fossilized footprints of a man inside of a footprint of a large dinosaur which could only occur if indeed they lived on earth at the same time. Also they have found stones thousand of years old that have carvings of specific breeds of dinosaur (some with 3 horns, others with long necks, other with large fins on their backs) which proves that early man were eye witnesses to living dinosaurs.
As for cavemen, think about this. Have you ever saw the skeleton of a man who live 300 years? 600 years? 900 years? Considering there are large concentrations of neanderthal skeleton around the middle east, coul be that these are the skeletons of humans who had aged a great deal? Just think about how gravity effects the body in 80 years... could you imagine the effects after 800?