No one truly knows how long after the asteroid impact the dinosaurs became extinct, but several studies in 2009 point to a possible number: around 300,000 years after the impact. For example, scientists uncovered marine sediments in Mexico that seem to contain at least 52 species of various animals, creatures that were found in younger rock. Another scientist claimed to have unearthed dinosaur bones in the American Southwest that date almost a half million years after the Yucatan impact. If this is true, scientists don’t believe that the dinosaurs actually survived in areas around the impact, but instead the creatures that survived in relatively unscathed areas later moved and recolonized in areas closer to the impact.