Dinosaurs ‘already doomed before giant meteorite hit’
DINOSAURS were already on the way out millions of years before being wiped out by a giant meteorite, scientists have found.
The number of dinosaurs began falling 76 million years ago after cooler temperatures began upsetting their food chain, according to a new study co-authored by an international team from centres including the University of Bristol.
Dinosaurs are believed to have met their maker 66 million years ago when a seven-mile wide asteroid struck what is now the Yucatan Peninsula in Mexico. But whether the giant reptiles were already on the decline has been fiercely debated.
Now, an international team of scientists has found evidence dinosaurs were doomed long before the fateful day.
Their decline allowed other species to rise to power, including mammals from which humans descended.
Lead author Dr Fabien Condamine at Centre National de la Recherche Scientifique in Montpellier, France, said: “We looked at the six most abundant dinosaur families through the whole of the Cretaceous, spanning from 150 to 66 million years ago, and found that they were all evolving and expanding and clearly being successful.
“Then, 76 million years ago, they showed a sudden downturn. Their rates of extinction rose and in some cases the rate of origin of new species dropped off.”
Co-author Dr Guillaume Guinot said they found evidence for decline before the asteroid impact.
He said: “It became clear the plant-eating species tended to disappear first, and this made the latest dinosaur ecosystems unstable and liable to collapse if environmental conditions became damaging.”
The researchers pored over more than 1,600 dinosaur records which had walked the four corners of the earth during the Cretaceous period.
They found their numbers had already begun dwindling up to 10 million years before the exctintion event took place.
Two main factors were identified which caused the dinosaurs to decline before the meteorite struck.
Co-author professor Mike Benton at the University of Bristol said: “It became clear that there were two main factors, first that overall climates were becoming cooler, and this made life harder for the dinosaurs which likely relied on warm temperatures.
“Then, the loss of herbivores made the ecosystems unstable and prone to extinction cascades.
“We also found that the longerlived dinosaur species were more liable to extinction, perhaps reflecting that they could not adapt to the new conditions on Earth.”
The decline of the dinosaurs 160 million years ago was a key turning point for other animal species who began their rise to “dominance”.
The findings were published in the journal