Uncovering Evidence of a 6th Mass Extinction
New fossil evidence is pointing to the possibility of a sixth mass extinction event in Earth's past, and this one may have helped usher in the largest "great dying" that that ever occurred. If that is right, the Permian period may have actually been hit with a two-punch knockout that caused more species loss than the infamous extinction of the dinosaurs.
It has long been known that about 252 million years ago, a massive Permian-Triassic extinction event occurred that wiped out more than 90 percent of all marine species and 70 percent of all land animals. This event, known as "the great dying," is famous among experts, as it's the only mass extinction that marked the end of even numerous insect species, which are traditionally the expected survivors of these disasters. It also marked the end of the Paleozoic era.
Causes of this event remain a relative mystery, but it is fairly certain that it would take a "perfect storm" of both sudden and gradual factors to lead to such complete destruction of life. Natural climate change, disease, sudden methane gas release, drastic volcanic activity, and your obligatory asteroid impact event could have all played a part. (Scroll to read on...)
Much of the evidence that would have betrayed the actual cause of the extinction has either by now been destroyed or is concealed deep within the Earth under many layers of rock. However, one researcher is now suggesting that another mass extinction on a smaller scale may have served as a precursor to the great dying.
Late paleontologist Jack Sepkoski, who first detailed the Earth's five major mass extinctions, has suggested that another extinction event occurred about eight million years before the great dying. However, this event happened exclusively in the tropics, ruling it out as a "mass extinction."
David Bond, at the University of Hull, wanted to revisit this concept in his recent work, finding that at the same time species were disappearing the tropics, marine life was dying in droves in the Arctic.
"We can now say this is a real global mass extinction," he announced at the recent meeting of the Geological Society of America (GSA) in Vancouver, Canada. (Scroll to read on...)
According to a GSA study detailing these findings, the fossil record Bond has uncovered in Spitsbergen, Norway and in Greenland suggests that more than 50 percent of all marine life died during the event, with some groups losing 80 percent of their diversity.
Bond suggests that this may have fatally weakened food webs across the globe, right before the world was hit with another series of disasters when it was down a mere eight million years later. In contrast, other mass extinctions have been separated by at least 50 million years, providing ample recovery time.
Bond is now calling for the earlier Permian event to be added to the list of mass extinctions that influenced Earth, making the "big five" the "big six."
However, paleobiologist Mike Benton of the University of Bristol, UK, told New Scientist that he thinks Bond might be jumping the gun.
"Bond's ideas are reasonable," he said, "but nobody has yet provided a detailed and thorough estimate of the severity of the extinction so it can be evaluated against the big five."
But it's important to note that Bond isn't done yet. Before his work, this potential sixth event was ranked as the tenth most impactful isolated extinction event. Now it looks to be more like the third most severe extinction event of marine life ever, eliminating nearly three-quarters of all trilobites - a type of marine anthropoid that was finished off in the great dying.
Bond is now analyzing Permian fossil data from Siberia, and thinks his proposal will be able to stand on its own.