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Extinction Theories We’re going to take a brief break from exhibit spotlights, then cover our Argentine dinosaurs during the month of September. This week we cover one of the most frequently asked questions about dinosaurs: how did they all die? Science does not yet have a definitive answer, but plenty of theories have been suggested—some much more plausible than others.

As bad as all that sounds, it gets worse: Chicxulub may have travelled with friends. Other impact craters from similar strata show that a number of cataclysmically large collisions may have followed Chicxulub like aftershocks, exacerbating an already dire ecological situation. Most scientists now agree that a catastrophic asteroid event must have played a significant role in the extinctions that doomed the rule of reptiles and paved the way for the age of mammals. It may not have doomed the dinosaurs completely, though: fossil evidence suggests the possibility (not proof) that some populations of dinosaurs may have survived as many as 2 million years after the impact.

Dozens of other theories have been put forward over the years—too many to fit in here. These represent the strongest currently accepted candidates for the smoking gun at the end of the Cretaceous, though in reality they all probably worked in concert to spell the dinosaurs’ doom, as well as that of roughly three-quarters of all species living at that time. Horrific as that sounds, it was only the third worst mass extinction on record: the worst came at the end of the Permian and killed off an estimated 83% of all species. That event has proven even more mysterious than the more famous K-T extinction we’ve just discussed. —Jeff Bond