BRISTOL, England, April 18 (UPI) -- A massive asteroid may have sealed the fate of the dinosaurs, but new research suggests the animals were already trending downward several million years prior.
Most scientists now agree that a large meteorite played a significant role in snuffing out the dinosaurs some 66 million years ago. A reanalysis of the fossil record, however, shows that dino species began disappearing faster than new ones emerged as early 50 million years before the asteroid apocalypse.
The latest research, conducted by a team of paleontologists from the University of Reading and the University of Bristol, suggests some groups of dinosaurs were fading faster than others. Sauropods, the long-necked plant-eaters, were in rapid decline, while the disappearance of theropod species, the group that includes T. rex, was more gradual.
Researchers, who detailed their work in the journal PNAS, say the findings indicate dinosaurs were being outcompeted by other species. As time went on, they were increasingly at an evolutionary disadvantage.
"While a sudden apocalypse may have been the final nail in the coffin, something else had already been preventing dinosaurs from evolving new species as fast as old species were dying out," lead researcher Manabu Sakamoto, a Reading paleontologist, said in a news release.
When an asteroid struck Earth 66 million years ago, it shrouded the planet in dust. A lack of sun and cool temperatures stunted plant growth and choked out the dinosaurs. Scientists believe an uptick in volcanic activity and shifting continental landmasses also played a role hastening the dinosaur's extinction.
What the latest research suggests is that the dinosaurs' disappearance in the wake of the asteroid strike wasn't a surprise. Their inability to cope with ecological change was already apparent, based on their failure to speciate fast enough.
Mammals were the benefactor of a world without dinosaurs, but the evolutionary history of the dino is proof that dominance doesn't last forever.
"Our study strongly indicates that if a group of animals is experiencing a fast pace of extinction more so than they can replace, then they are prone to annihilation once a major catastrophe occurs," Sakamoto added. "This has huge implications for our current and future biodiversity, given the unprecedented speed at which species are going extinct owing to the ongoing human-caused climate change."