Dinosaurs might have survived the catastrophic asteroid impact that ended their reign had it slammed into earth at a "more convenient time", a scientist has claimed. And if it had, humans would probably not exist.
The violent collision 66 million years ago, which occurred in the area that is now Mexico, triggered tsunamis across the oceans, caused powerful earthquakes and released enough heat to start many fires.
Material thrown into the air descended as acid rain and blocked the sun's warmth, cooling the earth temporarily, perhaps by tens of degrees Celsius. A thick blanket of dust that was thrown up darkened the globe.
The devastation wrought by the impact almost certainly explains the sudden death of the land-based dinosaurs, according to fresh analysis of the latest data.
But one scientist on the team said the reptiles might have prevailed had the asteroid struck earlier or later than it did.
Edinburgh University palaeontologist Steve Brusatte was part of a team of researchers who reviewed the evidence on dinosaur extinction. They studied work done on prehistoric climate, changes in sea levels, volcanic activity and biodiversity, before concluding that the asteroid was the prime culprit. "The asteroid almost certainly did it, but it just so happened to hit at a bad time when dinosaur ecosystems had been weakened by a loss of diversity," Brusatte said. "If it had hit a few million years earlier or later, dinosaurs probably wouldn't have gone extinct."
The scientists' report found that while the dinosaurs were largely faring well at the time of the asteroid impact, the big plant-eating types - including the horned triceratops and duck-billed dinosaurs - had suffered a loss of biodiversity. There were fewer animals at the bottom of the food chain.
Dinosaur biodiversity rose and fell throughout their time on earth over 150 million years. Brusatte said he suspected that, given a few million years more, the large plant-eaters would have recovered, making the ecosystem more robust.
"If the asteroid didn't hit, I have no reason to believe they'd have gone extinct," he said. "And if dinosaurs didn't go extinct, then mammals would have never had their opportunity to blossom. So if it wasn't for that asteroid, then humans probably wouldn't be here."