6000 years ago all living things were vegan, dinosaurs, tigers, lions all lay down with the lambs and ate only vegetation.

Whatever you are smoking, put it down and back away. Seriously dude, where did you pull that one out of? There have always been carnivores and herbivores, before them there were plants, before those were algae, bacteria, molds, and fungus. Before that the earth was just a spinning molten mass with gravity. At no time did man kind harness dinosaurs. They ate what they could find. Plants and fruits and insects at first , then smaller animals and fish. Tigers and lions never relied solely on vegetation to survive.