Mass extinctions "change evolution rules"

Posted By: Abdul Nisar
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Washington, Sept 5 (ANI): A new study from Macquarie University has analyzed why global mass extinctions occur - whether they are just short-term diversions in life's preordained course, or spring up completely new paths of evolution.

"Mass extinction fundamentally changes the dynamics. It changes the composition of the biosphere forever. You can't simply predict the winners and losers from what groups have done before," Wired News quoted paleobiologist John Alroy as saying.

Some believe that, in the absence of extinctions, species would diversify endlessly. Others argue that each taxonomic group had limits; once it reached a certain size, each branch would stop growing.

Palaeontologist Jack Sepkoski proposed that, by looking at the rate at which each group produced new species, one could predict the winners and losers of each mass extinction's aftermath. Groups that diversified rapidly would flourish. Their destiny was already established.

"It's a clockmaker vision of evolution. Each group has fixed dynamics, and if there's an extinction, it just messes it up a bit," said Alroy.

"That's what I'm challenging in this paper. There are limits, and that's why we don't have a trillion species. But those limits can change," he said.

Alroy crunched marine fossil data in the Paleobiology Database, which gathers specimen records from nearly 100,000 fossil collections around the world.

He didn't find Sepkoski's correlation between pre-mass-extinction diversity rates and post-extinction success. Each mass extinction event seemed to change the rules. Past didn't indicate future.

But paleontologist Charles Marshall of the University of California, Berkeley noted that Alroy's statistical methods still need review by the paleobiology community.

"There will be no immediate consensus on the details of the pattern of diversity," he wrote. But "the pieces are falling into place."

Alroy's analysis suggests that the future is inherently unpredictable, that what comes next can't be extrapolated from what is measured now.

"The current mass extinction is not going to simply put things out of whack for a while, and then things will go back to where we started, or would have gone anyway," said Alroy. (ANI)

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