Mammals Were Almost Completely Wiped Out Alongside The Dinosaurs

Gobiconodon, one of the largest known mammals of the Early Cretaceous. Ghedoghedo/Wikimedia Commons; Public Domain

The asteroid that proved to be the coup de grâce to the non-avian dinosaurs almost finished off our own ancestral lineage too, according to new research. Writing in the Journal of Evolutionary Biology, a team of researchers note that up to 93 percent of mammal species also went extinct when the spacefaring apocalypse arrived on Earth.

By examining the published fossil record from western North America from 2 million years prior to the end-Cretaceous mass extinction event, to 300,000 years afterward, the researchers were able to ascertain roughly how many species evolved and compare it to how many became extinct. Although many previous studies assumed that mammals would have been affected by the asteroid impact, few would have predicted that they were almost completely wiped out by it.

“Because mammals did so well after the extinction, we have tended to assume that it didn't hit them as hard,” Nick Longrich, an evolutionary biologist at the University of Bath and the study’s lead author, said in a statement. “However our analysis shows that the mammals were hit harder than most groups of animals, such as lizards, turtles, crocodilians.”

content-1466419912-alphadon-sp-muse.jpgAlphadon, a small mammal living during the Late Cretaceous, alongside the famous T. rex. MUSE - Science Museum of Trento; Wikimedia Commons; CC BY-SA 3.0

Despite this zoological hammering, the mammals then went on to take over Earth in much the way the dinosaurs did hundreds of millions of years earlier. It’s a remarkable thought that every single mammal alive today evolved from the 7 percent that made it through the asteroid impact, living alongside birds, who are of course dinosaurian descendants. The key to survival, it seems, was the ability of mammals to adapt.

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