A new study found that mammals were on the brink of extinction after an asteroid hit earth, but have been better at recovery.
An asteroid caused the extinction of dinosaurs, at least his is the most popular theory. New research says that it was not only dinosaurs that suffered in a big way. The same asteroid wiped out over 90 percent of mammal species. The asteroid hit earth in the Cretaceous period 66 million years ago. This is much more than thought before.
Researchers at the Milner Centre for Evolution at the University of Bath reviewed all mammal species known from the end of the Cretaceous period in North America. Their results showed that over 93 percent became extinct across the Cretaceous-Paleogene (K-Pg) boundary. The study also found that mammals recovered far more quickly than previously thought.
The scientists analyzed the published fossil record from western North America from two million years before the Cretaceous-Paleogene boundary, until 300,000 years after the asteroid hit. They compared species diversity before and after this extinction event to estimate the severity of the event and how quickly the mammals recovered.
Dr Nick Longrich from the Milner Centre for Evolution, in the University of Bath’s Department for Biology & Biochemistry, explained: “The species that are most vulnerable to extinction are the rare ones, and because they are rare, their fossils are less likely to be found. The species that tend to survive are more common, so we tend to find them."
“The fossil record is biased in favor of the species that survived. As bad as things looked before, including more data shows the extinction was more severe than previously believed,” he added.
The researchers say this explains why the severity of the extinction event was previously underestimated. With more fossils included, the data includes more rare species that died out.
Following the asteroid hit, most of the plants and animals would have died, so the survivors probably fed on insects eating dead plants and animals.
With so little food, only small species survived. The biggest animals to survive on land would have been no larger than a cat. The fact that that most mammals were small helps explain why they were able to survive.
The recovery took just 300,000 years, a short time in evolutionary terms.
Dr Longrich added: “Because mammals did so well after the extinction, we have tended to assume that it didn’t hit them as hard. However our analysis shows that the mammals were hit harder than most groups of animals, such as lizards, turtles, crocodilians, but they proved to be far more adaptable in the aftermath. It wasn’t low extinction rates, but the ability to recover and adapt in the aftermath that led the mammals to take over.”
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The study by researchers at the Milner Center for Evolution at the University of Bath and published in the Journal of Evolutionary Biology.