December 4, 2012 12:06 pm
World’s Greatest Extinction May Have Actually Been Two Extinctions in One
Life on Earth during the Permian era was quite complex. This little guy is a Dimetrodon. Photo: Stephen Woods
Life on Earth began at least 2.7 billion years ago, though maybe as much as 3.5 billion years ago, when simple microscopic organisms arose from the ooze. And, roughly 250 million years ago, the Earth came as close as it has ever been since to turning into a burning, lifeless world. Known as the Permian-Triassic boundary extinction, or, more dramatically, the Great Dying, 90 percent of all marine life, and 70 percent of all land animals were wiped out when the temperature soared and the oceans acidified.
What exactly caused the Great Dying is a matter of considerable debate: some people think volcanic eruptions did it, some think a meteorite did it. Some think the oceans ran out of oxygen, or that they became too acidic.
In a new study published in the journal Nature Geoscience, researchers found that the Permian-Triassic extinction may not have been one massive, life-destroying event, but two, spaced apart by an 180,000 year “recovery phase.”
Looking at fossil and sediment samples from the ancient continent South China, and tracking the appearance of 537 different species, the researchers found that the PT extinction took place in two waves. They found that the first wave wiped out all but a third of the identified species, and those that survived often did so within a much narrower range of habitats. The second pulse finished off the bulk of these survivors, and a large chunk of the new species that managed to crop up during the downtime.
The researchers think that the two-pronged approach to nearly wiping out all life on Earth had a big role in shaping the species that carried on into the future. Rather than just being required to withstand one mighty blow, the creatures needed to survive, adapt to their new world and then survive again.
The idea that the world’s worst extinction may not have been one event, but two, means that scientists can have a little more wiggle room when trying to understand what exactly could have caused such a mess. The authors of the new study suggest that, based on which species were wiped out, the first wave was likely either caused by volcanic winter or rampant ocean acidification. The second pulse, they say, was caused by extensive anoxia—where “a spread of oxygen-poor conditions” led to a collapse of deep-ocean life.
More from Smithsonian.com:
Earth’s Worst Extinction May Have Been Key to Dinosaur Origins
The Top 10 Greatest Survivors of Evolution
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Imagine we find traces of civilization during that period… lol. I wonder what the Quaternary extinction event and the mass extinctions occurring today will look like in another 250 million years…
The Permian was the most biodiverse period in the earths history, we have still yet to recover, (and probably never will).
Comment by Ikelos — December 4, 2012 @ 5:06 pm
Don’t put a picture of a large dinosaur for an article about the extiction event that happened 190 million years before dinoaurs were the dominant organisms.
Comment by vinny — December 5, 2012 @ 1:16 pm
That meant to say 190 million years before the dinos bit the bullet
Comment by vinny — December 5, 2012 @ 1:17 pm
Hi Vinny,
It’s a common misconception, but dimetrodons were actually not dinosaurs–they were reptiles that lived in the late Permian era.
Comment by Colin Schultz — December 5, 2012 @ 1:22 pm
I agree with Ikelos… What if we were to find traces of civilization from that period, or even from just 1 million years ago?
The more I learn about the beginnings of civilization (Ancient Egypt, Gobekli Tepe, etc.), the more I am beginning to believe that something is wrong with the currently widely-accepted timeline. Indeed, it appears that the origins of civilization occurred much earlier than is now widely accepted. Such an assumption, however, begs the question: What happened to those civilizations? I read recently that all human beings are the descendants of only 10,000 ancestors. What if there were great civilizations prior to the extinction event that nearly wiped out humans?
Comment by Joe — December 5, 2012 @ 1:33 pm