Fossil evidence of several species has been found linking modern-day whales to their ancient land mammal ancestors. this series of fossils provides evidence for adaptive radiation because the whales retained most of the skeletal shape and structure of their ancestors gradualism because one species evolved slowly and steadily over time by small genetic and physical changes co-evolution because the different mammals evolved together to interact with the changing environment punctuated equilibrium because one species evolved into several related species over a long period of time