Tue, Jul 29, 2014 page7

• Dinosaur extinction could be a case of ‘bad timing’

  YUCATAN CRATER: Edinburgh University experts say the asteroid that hit 66 million years ago arrived at a time when biodiveristy loss had weakened ecosystems

  • The Guardian, LONDON
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  Dinosaurs might have survived the catastrophic impact that ended their reign had the devastating asteroid that slammed into the Earth arrived at a “more convenient time,” a scientist has claimed. As a result 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 also blocked the sun’s warmth, cooling the Earth temporarily, perhaps by tens of degrees Celsius.

  

  A model of a Velociraptor stands in the forest at the Karpin Abentura park in the Karrantza Valley, outside Bilbao, Spain, on Saturday. The park, housing wildlife and model dinosaur areas, reopened on Saturday following damage caused by recent heavy rains.

  Photo: Reuters

  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.

  However, one scientist on the team said the beasts might have prevailed had the asteroid struck earlier or later than it did.

  Steve Brusatte, a paleontologist at Edinburgh University, was in an international team of researchers who reviewed the evidence on dinosaur extinction.

  The group looked at work done on prehistoric climate and temperatures, changes in sea levels, volcanic activity and biodiversity, before reaching a consensus 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 the asteroid had hit a few million years earlier, or a few million years later, then dinosaurs probably wouldn’t have gone extinct.”

  The scientists’ report, published in Biological Reviews, found that while, largely, the dinosaurs were 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.

  “The decline made those ecosystems at the very end of the Cretaceous [period], when the asteroid hit, considerably more vulnerable to collapse than those ecosystems that existed even a few million years before,” Brusatte said.

  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.

  The asteroid, which was about 9.65km across, struck the Yucatan Peninsula and left a crater, the Chicxulub, measuring 19km deep by 199.5km wide.

  The collision wiped out about 80 percent of the Earth’s species, though some dinosaurs survived to become the direct ancestors of birds.

  “If the asteroid didn’t hit, I have no reason to believe they’d have gone extinct. 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,” Brusatte said.
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