A study published in the scientific journal Nature Communications reveals that dinosaurs were already in decline for up to 10 million years before the asteroid collided with Earth and sealed the fate of the giant reptiles about 66 million years ago.
“We’ve seen the six most abundant dinosaur families across the Cretaceous [entre 145 e 65 milhões de anos atrás], and we found that everyone was evolving and expanding and clearly succeeding. Then, 76 million years ago, they showed a sudden decline. Extinction rates have increased and, in some cases, the rate of origin of new species has dropped”, says researcher Fabien Condamine, from the Institute of Evolution Sciences in Montpellier, France, the study’s main author, cited by the University of Bristol, UK, who also participated in the survey.
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Models based on Bayesian inference were used [método estatístico que inclui suposições] to explain various types of uncertainties, such as incomplete fossil records, dating, and evolutionary models. Each of the models was run millions of times to consider all possible sources of error and find out if the analyzes would converge to a more likely outcome.
“In all cases, we found evidence of decline before the impact of the bolide. We also looked at how these dinosaur ecosystems functioned and it became clear that plant-eating species tended to disappear first, and this made their environment more unstable and prone to collapse if environmental conditions worsened,” explains researcher Guillaume Guinot , from the Montpellier Institute of Evolution Sciences, one of the authors of the study, also cited by the British university.
Scientists have evaluated more than 1,600 records of dinosaurs that lived in the Cretaceous period and that came from North America, Mongolia, China and other areas.
“In the analyses, we explore different types of possible causes for the decline of dinosaurs. It was clear that there were two main factors. First, the general climate was getting colder, making life more difficult for the dinosaurs, who depended on high temperatures. So, the loss of herbivores left the ecosystem unstable and prone to mass extinction”, explains researcher Mike Benton, from the University of Bristol, who also participated in the study and was mentioned on the educational institution’s website.
This was a key moment in the evolution of life. The world was dominated by dinosaurs for over 160 million years, and as their species dwindled, other groups began to take over, including mammals.
According to the research, the dinosaurs were so large that they were probably unaware of the existence of the small furry mammals that lived in the undergrowth. But the species of our ancestors began to increase before the giant reptiles had disappeared. After the impact on Mexico’s Yucatán Peninsula, mammals came to dominate the planet.
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