When the asteroid hit, it conspired with massive, prolonged volcanism to significantly and rapidly alter the climate. The volcanism initially caused global cooling, before the massive carbon dioxide outflow warmed the planet. When the asteroid hit, it almost immediately darkened the skies, and the world cooled once more.
These low light levels and huge climatic fluctuations severely impacted vegetation’s ability to photosynthesize, and edible plants across the world died out. This killed off the herbivorous dinosaurs, which in turns sent shockwaves through the food chain. Many mammals, who at the time were often opportunistic omnivores – although some were large enough to eat dinosaurs – also died out this way.
Only the small survived, as they required the least amount of food to make it through the day. It’s likely they scavenged on dead plants and animals until life on Earth began to truly recover.
This adaptability proved to be a huge boon for the mammals: The team’s research suggested it only took them 300,000 years to recover from one of the worst mass extinction events in the history of the world. “It wasn't low extinction rates, but the ability to recover and adapt in the aftermath that led the mammals to take over,” Longrich added.
R. robustus, a mammal large enough to feed on small dinosaurs. Nobu Tamura/Wikimedia Commons; CC-BY 3.0
This research comes hot on the heels of another study, which revealed that the dinosaurs were in decline 50 million years before they officially bit the bullet; although no clear cause for this decline could be pinpointed, the researchers suspected the rise of opportunistic mammals, those that could steal dinosaurian resources, may have been to blame.
A second study also looked at how mammals suffered during the asteroid impact 66 million years ago, and it concluded that, indeed, many of them went extinct at the boundary. However, it also states that it took mammals several million years to recover from this event – a stark contrast to this new study, which suggests it was far more rapid.