# Permian mass extinction - suffocation?



## Brian G Turner (Sep 12, 2003)

Here's an interesting article, continuing a long fascination with news about lastest theories on mass extinctions in the geological record:

http://www.newscientist.com/news/news.jsp?id=ns99994138

*Suffocation suspected for greatest mass extinction* 

The oxygen-starved aftermath of an immense global belch of methane left land animals gasping for breath and caused the Earth's largest mass extinction, suggests new research.

Greg Retallack, an expert in ancient soils at the University of Oregon in Eugene, says his theory also explains the mysterious survival of a barrel-chested reptile that became the most common animal on the planet after the end of the Permian period, 251 million years ago.

Paleontologists have long puzzled over the mass extinction at the end of the Permian. There is no evidence for a large asteroid impact, but sharp changes in carbon isotope ratios indicate something triggered massive releases of frozen methane hydrates from under the sea floor and in permafrost. 

Methane is a strong greenhouse gas, and it reacts with atmospheric oxygen to produce carbon dioxide, which also would turn up the global thermostat. This dramatic climate shift has been blamed for the extinctions.

But Retallack was not convinced after working in the Karoo desert of South Africa. Fossils there show that the extinction claimed 88 per cent of late Permian genera. Yet the fossil soils he examined did not show evidence of the tremendous climate change needed for the wipe out.


*Plummeting oxygen* 


Inspiration struck when Retallack saw a study of long-term effects of the methane release. Bob Berner of Yale University calculated that a cascade of effects on wetlands and coral reefs would have reduced oxygen levels in the atmosphere from 35 per cent to just 12 per cent in only 20,000 years - a fleeting moment in geological time.

Retallack knows the effects of low oxygen levels all too well. "I've just about died of mountain sickness at [the equivalent of] 12 per cent oxygen" while working at high altitudes, he told *New Scientist*. "I know exactly what it's like."

Lungs used to higher oxygen levels strain desperately for oxygen, and fill with fluid. The lack of oxygen would have left most Permian land animals gasping for breath, suffering from nausea, headaches, and inflamed lungs. Marine life would have suffocated in the oxygen-poor water.


*Short nostrils* 


Yet the ungainly meter-long reptile _Lystrosaurus_ survived because it had evolved to live in burrows, where oxygen levels are low and carbon dioxide levels high. It had developed a barrel chest, thick ribs, enlarged lungs, a muscular diaphragm and short internal nostrils to get the oxygen it needed. Retallack says Sherpas have developed some similar adaptations by living at high altitudes for generations.

While most Permian animals died gasping for breath, _Lystrosaurus_ spread rapidly. In some areas, it accounts for 90 per cent of the fossils found after the extinction. 

Oxygen depletion also could explain why coal swamps and coral reefs disappeared for millions of years after the extinction, says Retallack, as both are highly sensitive to oxygen levels.

He acknowledges that more work is needed to confirm his theory, and suggests looking at how _Lystrosaurus_ changed as it spread in the post-methane world. He predicts a thick backbone would be an adaptation for low oxygen.

Journal reference: _Geological Society of America Bulletin_ (vol 115, p 1133)


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## The Ace (Jun 6, 2006)

Do you mean that the world farted ?  I suppose there could be something in that.


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## kyektulu (Jun 6, 2006)

*That is fascinating Brian, thanks for the info!*


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