How do you know, dinosaurs populated the Earth before man appeared and the fall of a meteorite caused a cloud of dust and gas that led to its extinction.. However, another element that could have ended is now up for debate: the cold. It is a study published in Nature Communications, signed by biologist Fabien Condamine, points out that the meteorite could have represented the coup de grace, but that dinosaurs, 65 million years ago, have already suffered from the planet’s cooling.
However, since the discovery of the gigantic impact crater in Mexico in 1980, there is no consensus in the scientific community about the object’s responsibility for its disappearance. “It’s a heated debate,” explained Condamine.
The data are not robust enough to validate one hypothesis or another: “The fossil record (dinosaur bones) is incomplete, in a poor state of conservation, some geographic areas like the tropics are poorly represented, some time periods are better recorded than others, “said the researcher at the National Center for Scientific Research (CNRS) of the Institute of Evolutionary Sciences in Montpellier, in southern France.
To correct these biases, the scientist and his team (made up of French, British and Canadians) used a new method of statistical modeling, which calculates the probabilities of causes based on the observation of common elements. They selected 1,600 fossils that belonged to six dinosaur families, including the iconic tyrannosaurs, triceratops and hadrosaurs.
Thanks to the method, researchers were able to estimate an age of appearance and extinction for each of the species, in a period that goes from 145 million years ago, at the end of the Cretaceous, to 66 million years, just before the disaster. . “We found a peak of diversity before 76 million years ago, with a high rate of creation of new species. And then a slow decline,” explained Condamine.
In a colossal period of 10 million years, the number of dinosaur species decreases, from fifty to less than twenty, 66 million years ago. The researchers compared these statistics with known environmental data (climate, marine or geological).
The results showed a perfect correlation with the climate curves: “As the rate of disappearance of species increases, in parallel, temperatures fall.“, analyzed the expert. This drop in temperatures, which caused the Earth to lose 7 to 8 degrees, coincides “exactly “with the decline of the dinosaurs.” At that time, it was much warmer, there were palm trees and mangroves to level the Bering Strait,” between Siberia and Alaska, Condamine continued.
Difficulties in the cold
Dinosaurs were not able to produce their own body heat like humans. They were highly dependent on their environment to feed, move and reproduce, and your metabolism certainly couldn’t adapt to the change.
Another important piece of information is that the first disappearances affected herbivores, about two million years before carnivores. Fewer herbivores – the food of carnivores – would have unbalanced ecosystems and led to the serial extinction of other dinosaur families, the study suggests.
It is in this context that a meteorite twelve kilometers in diameter hit the Earth. Already weakened, the kingdom of these giants has not recovered from the cataclysm, unlike other small mammals.
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