A new study has found that over 90 per cent of mammal species were wiped out by the same enormous space rock that killed the dinosaurs 66 million years ago.
Researchers 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 per cent became extinct across the Cretaceous-Paleogene (K-Pg) boundary, but that they also recovered far more quickly than previously thought.
The scientists analysed 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. The extinction rates were much higher than previous estimates based on more limited data sets.
Dr Nick Longrich explained said that 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.
He added, "The fossil record is biased in favour of the species that survived. As bad as things looked before, including more data shows the extinction was more severe than previously believed."
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.
Surprisingly, the recovery from the extinction took place differently in different parts of the continent. The species found in Montana were distinct from those in nearby Wyoming, for example.
The study is published in the Journal of Evolutionary Biology.
