Without asteroid, dinosaurs would have continued to dominate Earth

An analysis of statistical models of dinosaur diversity shows that they were not in decline when they were extinct by an asteroid struck 66 million years ago.

Researchers at the University of Bath and the Natural History Museum say that had the impact not taken place, dinosaurs could have continued to dominate Earth.

Dinosaurs were widespread around the world by the time of the asteroid impact in the late Upper Cretaceous, they occupied every continent on the planet, and were the dominant animal form in most terrestrial ecosystems.

However, it is still controversial among paleobiologists whether the diversity of dinosaurs was in decline at the time of their extinction.

To answer this question, the research team put together a set of different dinosaur family trees and used statistical models to assess whether each of the major dinosaur groups could still produce new species today.

Their study, published in the journal Royal Society Open Science, found that dinosaurs were not in decline before the asteroid impact, which contradicts some previous studies. The authors also suggest that if the impact had not occurred, dinosaurs could have continued to be the dominant group of land animals on the planet.

The study’s first author, doctoral candidate Joe Bonsor, said in a statement: “Previous studies by others have used various methods to conclude that the dinosaurs would have gone extinct anyway because they were in decline. towards the end. from the Cretaceous period.

“However, we show that if you expand the dataset to include more recent dinosaur family trees and a larger set of dinosaur types, the results don’t really point to this conclusion; in fact, only half of ‘between them do. ” .

It is difficult to assess the diversity of dinosaurs due to gaps in the fossil record. This may be due to factors such as which bones are stored as fossils, how much access fossils have to the rock to allow excavation, and where paleontologists look for them.

The researchers used statistical methods to overcome these sampling biases, by examining the speciation rates of dinosaur families rather than just counting the number of species in the family.

Joe Bonsor said: “The main point of our article is that it’s not as simple as looking at a few trees and making a decision – the inevitable large biases in the fossil record and lack of data can often show a decline. cash, but that may not reflect the reality of the moment.

“Our data currently does not show that they were in decline, in fact certain groups like hadrosaurs and ceratopsians were thriving and there is no evidence to suggest that they would have been extinct 66 million years ago if the ‘extinction event had not taken place. “

While mammals existed at the time of the asteroid impact, it was only thanks to the extinction of the dinosaurs that cleared the niches, allowing mammals to fill them and then take over the planet.