The prehistoric asteroid that destroyed the dinosaurs nearly extinguished mammals as well.
A study by researchers at the Milner Centre for Evolution published in the Journal of Evolutionary Biology showed that more than 93% of mammals became extinct around the same time as the dinosaurs.
But they also bounced back quicker than we previously thought.
A cosmic catastrophe
The researchers analyzed fossil records from western North America from around 68 million years ago to 65.7 million years ago, around the time scientist believe the deadly asteroid struck. To figure out just how serious this whole asteroid thing was, and how quickly species bounced back, they compared species diversity before and after this extinction event.
Scientists hadn't realized just how cataclysmic this asteroid was for mammals. That's because the species most likely to become extinct were the rare ones. But because these species are so rare, so are their fossils.
"The fossil record is biased in favour of the species that survived," said Nick Longrich from the Milner Centre for Evolution, in a University of Bath press release. "As bad as things looked before, including more data shows the extinction was more severe than previously believed."
According to the press release, most of the plants and animals would have died when the asteroid hit. Whoever was left over probably fed on insects eating the corpses of animals and plants. Since food was so scarce, only the smallest species could survive - the biggest animals would have been "no larger than a cat."
The great comeback
Fortunately, we mammals are a resilient bunch. In fact, in terms of diversity, what didn't kill us made us stronger.
In just 300,000 years, the mammals were able to recover, "not only gaining back the lost diversity in species quickly but soon doubling the number of species found before the extinction," the press release says.
And, according to Longrich, in the aftermath of the event, there was actually "an explosion of diversity." He thinks that it was this "explosion" that helped to drive the recovery. With so many species evolving in different directions in different parts of the world, he said, evolution was more likely to "stumble across evolutionary paths."
"It wasn't low extinction rates, but the ability to recover and adapt in the aftermath that led the mammals to take over," Longrich said.