Why Did Dinosaurs Die Out?
For about 160 million years, dinosaurs were the largest and most successful animals on land. Then about 65 million years ago, these huge archosaurs died out along with pterosaurs, mosasaurs, and many other reptiles. Mammals then became the dominant animals on Earth. Scientists have developed many theories to explain dinosaur extinction. The two major theories involve (1) gradual climate changes and (2) the collision of an asteroid with Earth. The first theory argues that, toward the end of the Cretaceous Period, the shallow seas dried up and the climate became more varied everywhere around the globe. Winters became too cold and summers too hot for dinosaurs to survive. Dinosaurs were too large to hibernate in dens, and they had no fur or feathers for protection against the cold. They also probably had difficulty cooling off in hot weather. Thus, death and extinction came as a result of gradually colder winters and hotter summers.
The huge reptiles called dinosaurs began to flourish on earth 180 million ears ago. But all these creatures seemingly died out about 60 million years ago. Why the dinosaurs vanished suddenly, after ruling the earth for some 120 million years, is a question that still puzzles scientists today. The most probable explanation is tha
