"I think there is a perception that when the asteroid smashed into the Yucatan Peninsula 66 million years ago, it hit a static world, something of a paradise in which dinosaurs had been thriving for millions of years," Brusatte said. "But the asteroid actually hit a planet that was experiencing a lot of turmoil."
Paleontologists may be coming to a consensus on how non-avian dinosaurs--which flourished for over 150 million years--bit the dust, but they still don't know why certain birds survived the end of the Cretaceous onslaught.
"A lot of dinosaurs really looked and behaved like birds," he said. "If we were standing around in the Cretaceous, I don't think we would have made a distinction between a Velociraptor-type dinosaur and a true bird, and that is true of these feathered dinosaurs: these things were basically birds, and the line between them and birds is an arbitrary one."
Many species of birds did go extinct around 66 million years ago--just not all of them--reminded Richard Butler of the University of Birmingham's School of Geography, Earth and Environmental Sciences. Butler was not a co-author of the new paper.
Some birds might have survived because they were small, had more offspring, or possessed certain other characteristics and behaviors that permitted their survival, Butler and Brusatte theorize.
They both think that, without the asteroid impact and all of the other climatic and environmental upheaval, dinosaurs would still be roaming the planet today.
"Given that mammals were only able to expand dramatically in diversity once the dinosaurs had been extinguished, I think it is very unlikely that humans would be around today without the dinosaur extinction," Butler said.
"I think there is a very real sense in which we owe our existence to the dinosaurs' doom."