Ideas, Inventions And Innovations Mammals Competing with Mammals in the Age of the Dinosaurs Slowed Diversity More Than Their Reptilian Competitors Scientists discover that dinosaurs were not the main competition for mammals during the time of the dinosaurs, challenging previously held ideas about evolution. New research finds dinosaurs were likely not the main competitors of mammals during the age of the dinosaurs. The ancestors of modern mammals during the age of the dinosaurs remained less diverse because of competition with other mammal groups. Research suggests extinction of other mam...