The fate of the dinosaurs was decided long before the asteroid. There was someone else dominating the land

At least that’s what the authors of the publication available in the pages claim Science advanceswhich analyzed the interactions of species and ecosystems at the time, before and after the collision. To do this, the researchers used fossils found in western North America dating from the end of the Cretaceous period to the beginning of the Paleogene period.

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In total, 1,600 fossils belonging to mammals, fish, birds, and flightless dinosaurs were studied. As it turns out, small terrestrial and freshwater organisms were more resilient and better equipped in the event of a crisis like the one that affected the flightless dinosaurs. In other words, mammals diversified before, not after, the asteroid impact.

As a result, while dinosaurs were relatively poorly adapted to changing conditions, mammals were characterized by greater versatility, being able to survive at different temperatures and based on different diets. This is surprising, because it was long assumed that mammals did not become dominant until after the dinosaurs became extinct. New research shows the opposite: the ground for change became fertile for them even before the crisis.

Dinosaurs were in crisis even before the unlucky asteroid hit Earth

As the researchers show, the diversity of large herbivorous dinosaurs gradually decreased, and in the period from 83.6 million to 61.6 million years ago, there was a decrease in their share of the food web. Mammals were on the other side of the barrier: they were prepared to survive in different ecosystems, and when sudden changes occurred due to an asteroid impact, their diversity led to survival.

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A particular limitation of the research that was done is the fact that the authors only considered fossils from one continent. In such conditions, it would be difficult to create a global picture that would show the reality of millions of years ago. The breakthrough, however, appears to be the information that mammals weren’t the ones to benefit so much from an asteroid impact that weakened the dinosaurs – they were simply better prepared for such a scenario.