About 66 million years ago, dinosaurs faced an asteroid that smashed into the Yucatan Peninsula that completely transformed the world, marked the end of the Cretaceous period, and killed off about 75% of the animal species. The only ones that survived was a small percentage of birds.
However, a new study found that the animals were already well on their way to extinction.
The study comes from Manabu Sakamoto from the University of Reading and found that the dinosaurs were disappearing at a much faster rate than new ones were appearing - for as long as 40 million years before the asteroid hit.
This information didn't come out before because everyone was looking at the raw numbers instead of investigating the key to this study - the rocks that housed the fossils. Some rocks were just better at preserving the fossils than others, which caused the numbers to skew.
Stephen Brusatte from the University of Edinburgh did the research on the rocks and found that “no evidence for a progressive decline in total dinosaur species richness.” Two groups in particular, the horned ceratopsians and the duck-billed hadrosaurs, were found to be declining at the quickest rate. “Recently, the idea that the dinosaurs were reigning strong has dominated the academic debate,” says Sakamoto.
This isn't strictly true. In fact, he worked on a family tree of dinosaurs, which, when complete, had 614 dinosaurs. They looked at the rates at which new species arose and older ones went extinct. “We’re not counting numbers of species throughout the history of dinosaurs, but of speciation events,” he explains.
The "long-necks" or sauropods went through the biggest decline. In the early Jurassic period, they were populous, but that ended about 114 million years ago, when they were losing species faster than they could replace them.
Meat eating dinosaurs fared slightly better. Some of the most famous dinosaurs, including Velociraptors and tyrannosaurs, populated the earth during the Cretaceous period. Still, they were going extinct at an alarming rate as well.
Just why this was happening is still unknown, though we do know there was intense volcanic activity and the sea levels fluctuated dramatically. “I think that dinosaurs were probably under stress for a very long time,” says Sakomoto.
“This isn’t to say that the dinosaurs were going extinct before the asteroid impact, but they were getting more vulnerable and susceptible to mass extinction says Sakomoto. And that’s relevant to us in the modern world. “We are putting a lot of pressure on modern species, and extinctions are happening at an unprecedented rate. If some kind of catastrophe occurs, it might be even more damaging than what we’re observing right now.”
“I love seeing big datasets and new methods thrown at some of these classic mysteries,” says Brusatte. “The result seems very robust, but I question what it means. Does that mean that dinosaurs were doomed to extinction, that they endured some kind of long death march before the asteroid impact finished them off, like a boxer knocking down their opponent with a light punch after several rounds of pummeling? I don’t think so.”
He suspects that the results will say more about the booms instead of the bursts. “That doesn't mean the economy is necessarily doomed; it just means things aren't growing as insanely fast anymore,” says Brusatte to The Atlantic.
“I think we sometimes have a tendency to overthink the dinosaur extinction, myself included,” Brusatte adds. “The way I see it; it came down to the asteroid. Simple as that. Diversity declines may have made dinosaurs somewhat more susceptible to the asteroid impact, but probably nothing was going to save them.”
This study also solidifies the fact that dinosaurs all didn't live during the same time. In fact, we live closer in time to the Tyrannosaurus than the Tyrannosaurus lived to the Stegosaurus - which is pretty weird if you think about it.