When an asteroid 12 kilometers (7.5 miles) wide struck Mexico’s Yucatan peninsula.
one spring day 66 million years ago, it brought an end to the age of the dinosaurs and caused the extinction of nearly three-quarters of Earth’s species.
Were the dinosaurs already extinct before the asteroid hit, as some scientists have suggested, with diversification halting and rates of evolution sputtering? An unequivocal “no” is the response, according to a recent study.
But were the dinosaurs already extinct, as some scientists have suggested, as diversity faltered and evolution rates slowed down?
According to a recent study that simulated food chains and biological niches in North America, the region of the world best covered in the fossil record from that period, the answer is categorically “no.”
The study examined the four million years between the end of the Cretaceous Period (18 million years) and the beginning of the Paleogene Period (4 million years), when mammals, with the exception of their bird ancestors, began to assert their dominance.
The researchers recreated the food chains and habitat preferences of land and freshwater vertebrates using more than 1,600 fossils.
These included characters like the enormous meat-eating T. rex, the Triceratops with three horns, the Ankylosaurus that resembled a tank, as well as crocodiles, turtles, frogs, fish, and other tiny mammals coexisted with the dinosaurs.
The researchers discovered that dinosaurs were well established in ecological niches to which they were well adapted.
Thus, according to ecologist Jorge Garca-Girón of the Universities of Oulu in Finland and León in Spain, lead author of the study published in the journal Science Advances, “the dinosaurs perished in their prime.”
However, according to Garca-Girón, mammals had already started laying the groundwork for their later ascent by expanding their ecological niches and developing more diverse diets, behaviors, and climate tolerances.
According to the study, dinosaurs continued to change and evolve as they neared the end of their dominance, with new species emerging and extinct ones going extinct.
More species of medium-sized herbivores were beginning to take the place of some of the larger plant-eaters, such as the horned and duck-billed dinosaurs.
Based on the fossil record of different dinosaur families, some prior study hypothesised that the biodiversity of dinosaurs had already begun to dwindle long before the asteroid hit.
According to Steve Brusatte, a palaeontologist at the University of Edinburgh and study co-author
“there has been this nagging feeling that dinosaurs may have been on their way out anyhow, in the middle of a long-term decline, when the asteroid put them out of their misery.”
We can state with confidence that dinosaurs were flourishing and had stable ecosystems until an asteroid abruptly wiped them off.
The dinosaurs’ high degree of climate and ecological adaptation may have been their downfall.
The quick change to a world to which the dinosaurs were so used caused everything to become chaotic, according to Brusatte.
According to palaeontologist and study co-author Alfio Alessandro Chiarenza of the University of Vigo in Spain,
“our study suggests that it was probably the interplay among many other ecological features, including their body size, diets, behaviours, and ecospace plasticity that prepared certain smaller animals for greater survival after the asteroid impact.”
Before the asteroid, mammals comprised the now-extinct multituberculates rodent-like group, as well as eutherians, metatherians, and placental cousins of today’s marsupials and placentals.
Following the mass extinction, new mammals appeared, including numerous true placental mammals, which include the majority of living mammals today, including whales, bats, aardvarks, and humans.
The range of ecological niches and body sizes among post-apocalyptic mammals increased quickly.
The supercontinent of Pangea is where both mammals and dinosaurs originated and started to evolve back in the Triassic Period, some 230 million years ago, according to Brusatte.
“From there, they went their separate ways, with mammals reduced to little proportions in the shadows and dinosaurs going for grandeur,” Brusatte continued.”
However, their fates would be bound together forever. When the asteroid impacted, there were mammals present. They were successful. Our forefathers confronted the asteroid.