A new study suggests that dinosaurs were already facing extinction before an asteroid hit the Earth 66 million years ago. Earlier research showed that some species were on the decline the last few million of years before impact. This new study reveals that it began millions of years earlier (about 120 million years ago) and affected more species than originally thought.
Though the dinosaurs evolved quickly during the tropical climate of the Triassic period (225 million years ago), they began to decline when the climate cooled and the sea levels shifted.
Researchers from Reading and Bristol Universities in the U.K. used statistical analysis of fossil records to track the rate at which dinosaurs were evolving and the rate at which they were going extinct. For 50 million years prior to the asteroid strike, more species were going extinct than those evolving.
The study states,
Here, for the first time to our knowledge, we apply a statistical approach that models changes in speciation and extinction through time. We find overwhelming support for a long-term decline across all dinosaurs within all three major dinosaur groups.
This decline, however showed that different species of dinosaurs emerged while others declined during different times. Long necked sauropod dinosaurs declined the fastest while the theropods’ decline was more gradual. Duck-billed dinosaurs were actually on the rise before the asteroid hit.
Dr. Manabu Sakamoto, a paleontologist and leader of the research from the University of Reading says,
The current widespread view is that dinosaurs were reigning strong right up to the impact that hit the Earth – and it’s the impact that drove their final extinction. And while that’s certainly true, what we found was that they were in the decline long before that. If they were reigning strong perhaps they would have fared much better than they did.
Co-author of the study, Professor Mike Benton of Bristol University says,
World climates were getting cooler all the time. Dinosaurs rely on quite warm climates and mammals are better adapted to the cold. So there might have been a switch over in any case without the asteroid impact.
In either case, dinosaurs appear doomed.