Dinosaurs would likely still be around today if the 6.2-mile-wide Chicxulub asteroid had crashed into Earth just a little while before or after it did, concludes an international team of some of the world's leading paleontologists.
In short, dinosaurs were victims of colossal bad luck, according to University of Edinburgh vertebrate paleontologist and evolutionary biologist Stephen Brusatte, who led the study that is published in the latest issue of Biological Reviews.
"The asteroid almost certainly did it," meaning wiped out the dinosaurs, he told Discovery News, "but it just so happened to hit at a bad time when dinosaur ecosystems had been weakened by a loss of diversity."
"If the asteroid hit a few million years earlier, when dinosaurs were more diverse, or a few million years later, when they had a chance to recover as they often had done before after diversity losses, then dinosaurs probably wouldn't have gone extinct," he said.
Brusatte and his team came to this conclusion after studying an updated catalog of dinosaur fossils to create a picture of how dinosaurs, and the environment, changed over the few million years before the asteroid struck what is now Mexico.
The researchers found that during the years prior to the asteroid hit, Earth was undergoing huge volcanic eruptions and extreme changes in temperature and sea level. The changes were, at least in some respects, interconnected. For example, major volcanic eruptions, especially in what is now India, likely affected global temperatures.
Tectonic events, such as mountain formation, also led to the disappearance of a large seaway that had covered much of the interior of North America during most of the Cretaceous.
All of these changes impacted dinosaur populations, with large plant-eating dinosaurs that were at the base of the food chain particularly experiencing a dramatic drop in number. This, in turn, would have weakened the entire dino ecosystem.