93% Mammals Wiped Out by the Same Asteroid that Killed Dinosaurs - Dispatch Weekly

A new study has shown that mammals would have been wiped out completely off the face of the Earth alongside dinosaurs when the asteroid hit Earth millions of years ago; however, mammals at the time were a little luckier than the dinosaurs for 7 per cent of mammals managed to survive.

A new study by researchers at University of Bath puts forward evidence that indicates that the asteroid that killed dinosaurs actually managed to wipe out 93 per cent mammal species at the time – a number that is significantly higher than previous estimates.

Published in the Journal of Evolutionary Biology researchers reviewed all mammal species known from the end of the Cretaceous period in North America from two million years before the Cretaceous-Paleogene boundary, until 300,000 years after the asteroid hit and came to the conclusion that only 7 per cent mammal species survived across the Cretaceous-Paleogene (K-Pg) boundary and despite this low survival rate, they recovered far more quickly than previously thought.

For the study, researchers looked at and 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.

Researchers explain that the species that are most vulnerable and prone to extinction were the ones that were particularly rare and because of this rarity, very rarely their fossils are found. The fossils that have been found are mostly of those species that were relatively abundant and 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.

Yet the researchers found that mammals also recovered more rapidly than previously thought, not only gaining back the lost diversity in species quickly but soon doubling the number of species found before the extinction. The recovery took just 300,000 years, a short time in evolutionary terms.

The authors add that one of the reasons why we have been assuming that mammals weren’t hit as bad as dinosaurs was the fact that mammals managed to recover at a rapid rate and adapted quickly to changing circumstances. 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.