Dinosaursthose big prehistoric creatures may have already been decreasing in population long before an asteroid crashed into the Earth, and killed them. Until now, it was thought that an asteroid, or meteorite, that hit the Earth 66 million years ago was the main reason the reptiles became extinct. But a new study finds that they may have already been decreasing in numbers millions of years before that. Dr. Manabu Sakamoto is a dinosaur expert a paleontologist at the University of Reading in the United Kingdom. He led the research in the new study. “We were not expecting this result,” Sakamoto said. The effect of the asteroid hitting the Earth is still considered the main reason for the dinosaurs’ final disappearance, Sakamoto said. But, he added, “it is clear that they were already past their prime in an evolutionary sense.” In other words, Sakamoto means that dinosaurs were already starting to disappear from the land before the asteroid struck the Earth.