(CNN) Dinosaurs were already on a slow decline for at least 50 million years before a massive meteorite smashed into Earth and exterminated them, according to new research.
It may sound cold, but here's how lead researcher, Dr. Manabu Sakamoto, palaeontologist from University of Reading in the UK described it: "It is clear that they [dinosaurs] were already past their prime in an evolutionary sense."
Dinosaur diversity was already dropping for millions of years. It didn't matter what type of dinosaur -- a T. rex or brachiosaurus -- they had all been on a decline, according to the research published Monday in the journal Proceedings of the National Academy of Sciences.
Researchers drew the conclusion after analyzing lineages on the dinosaurs using fossil information and computing statistics.
"All the evidence shows that the dinosaurs, which had already been around, dominating terrestrial ecosystems for 150 million years, somehow lost the ability to speciate fast enough," said Professor Mike Benton of the University of Bristol, one of the co-authors in a press release statement. "This was likely to have contributed to their inability to recover from the environmental crisis caused by the impact."
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It is widely believed that a massive asteroid struck into the Gulf of Mexico 66 million years ago, with its impact producing tons of dust, blackening out the sun, and eventually killing all the plants and dinosaurs on Earth. But it had been a mystery whether dinosaurs were thriving before the asteroid hit.
"While a sudden apocalypse may have been the final nail in the coffin, something else had already been preventing dinosaurs from evolving new species as fast as old species were dying out," said Sakamoto. "This suggests that for tens of millions of years before their ultimate demise, dinosaurs were beginning to lose their edge as the dominant species on Earth."
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Dinosaurs could've been troubled due to environmental changes on the planet as the continents broke up, sea levels rose and more volcanoes got active. This could've left dinosaurs in fragmented habitats with limited opportunities to reproduce, according to researchers.
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But what was destructive for dinosaurs ultimately ushered in a new era for mammals -- and humans.