Dinosaurs were already in decline before the asteroid

The impact of a huge asteroid more than 65 million years ago in what is now the Mexican province of Yucatán is, according to most of the scientific community, the main cause of the extinction of the dinosaurs.

The brutal crash triggered a series of catastrophic events that changed Earth’s climate and wiped out most life at the time. However, an international team of researchers believes that the hitherto kings of creation were already in decline ten million years before receiving the death blow.

dinosaurs

As explained in the magazine ‘Nature Communications’, the six most abundant families of Cretaceous dinosaurs were expanding smoothly until 76 million years ago, when their extinction rates suddenly increased. At the same time, the appearance of new species decreased.

The team used Bayesian modeling techniques to take into account various types of uncertainties, such as incomplete fossil records, doubts in the dating of fossils, or uncertainties in evolutionary models. Each of the models was run millions of times to account for all of these potential sources of error.

“In all cases, we found evidence of the decline (of the dinosaurs) before the impact of the fireball”says Guillaume Guinot, from the Institute of Evolutionary Sciences in Montpellier. «We also looked at how these dinosaur ecosystems functioned, and it became clear that herbivorous species tended to die out first, and this made the last dinosaur ecosystems unstable and likely to collapse if environmental conditions became damaging.”Explain.

For Phil Currie, co-author of the study, from the University of Edmonton (Alberta, Canada), “the decline of the dinosaurs in their last ten million years makes sense and, in fact, this is the best-sampled part of their fossil record”. The researchers used more than 1,600 carefully reviewed Cretaceous dinosaur records.

colder climates

As for what could have caused this decline, Mike Benton of the University of Bristol’s School of Earth Sciences points to two main factors: “First, that climates in general were getting colder, and this was making life difficult for dinosaurs, which probably depended on warm temperatures.”Explain.

The second has to do with the loss of herbivores. This caused “That ecosystems were unstable and prone to cascading extinction. We also found that longer-lived dinosaur species were more prone to extinction, perhaps reflecting their inability to adapt to new conditions on Earth.”Add.

This was a key moment in the evolution of life. The world had been dominated by dinosaurs for more than 160 million years, and as they declined, other groups began to dominate, including mammals.

“The dinosaurs were mostly so big that they probably barely knew the little furry mammals were out there in the bush. But mammals began to increase in number of species before the dinosaurs disappeared, and then, after the impact, they had the opportunity to build new types of ecosystems that we see today “say the researchers. The fall of the biggest was our chance.

Font: ABC

Reference article: https://www.abc.es/ciencia/abci-dinosaurs-were-decline-before-impact-asteroid-202106291908_noticia.html#ancla_comentarios