ANOTHER Mass Extinction?! Compelling Proof of Past Mass Die-off
As far as scientists know, there have been a grand total of five mass extinctions over the last 500-million years - world-changing events during which the great majority of Earth's life was eliminated to make way for new organisms and evolutionary paths. However, for several decades, some experts have suspected that a 6th mass extinction existed among these "Big Five." Now researchers are claiming to have found extremely compelling proof of its existence.
It has long been known that 252 million years ago, a suspected "perfect storm" of dooms-day scenarios including disease, massive volcanic eruptions, and even you obligatory asteroid impact resulted in the extinction of 90 percent of all marine species and 70 percent of all land animals.
By comparison, the 200-million-year-old end-Triassic mass extinction (caused by a toxic turn in ocean chemistry) killed only 50 percent of all plant and animal life. And the exceptionally famous Great Impact event that wiped-out the dinosaurs (and a surprising number of mammals) left a stunning number of marine and insect species untouched.
How Could Five Mean Six? (To jump to new findings click here)
That's what makes the earlier event, known as "the Great Dying," the most infamous of the Big Five. Not only does it boast a bafflingly high extinction rate, but it's the only mass extinction that marks the end of even numerous insect species, which are traditionally the ultimate survivors.
Nature World News previously reported that, for the last few decades, experts have suggested a 6th world-changing event must have closely preceded the Great Dying - a theory first proposed by a man who helped confirm the existence of the Big Five - the late paleontologist Jack Sepkoski. (Scroll to read on...)
Last October, researcher David Bond, at the University of Hull, revisited this theory, finding more evidence that marine mass extinctions occurred simultaneously in the tropics and Arctic 260-million years ago. He argued that it was this smaller mass-extinction that weakened global food-webs and made the Earth vulnerable enough for the Great Dying to become such a crippling event, 8-million years later.
However, at the time, there was a lot of doubt that this 6th event was as important as Bond argues.
"Bond's ideas are reasonable," paleobiologist Mike Benton of the University of Bristol, UK, told New Scientist, "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."
The mid-Permian 'Proof'
What skeptics were waiting for, it seems, was proof that this 6th event impacted terrestrial life as well, and made such an impact on a greater global scale. Now, according to a study recently published in the journal Proceedings of the Royal Society B, that evidence has been found.
The study details how 260 million years ago, when marine life was biting the dust elsewhere, a diverse group of early mammal-like reptiles called dinocephalians - the largest land-living animals of the time - were also vanishing.
"A mid-Permian extinction event on land has been known for some time but was suspected to have occurred earlier than those in the marine realm. The new date suggests that one event may have affected marine and terrestrial environments at the same time, which could mean its impact was greater than we thought," Michael Day, a researcher with Wits University, explained in a recent statement. (Scroll to read on...)
Day and his colleagues reportedly found their 'proof' in the form of carefully dated fossil samples from the Karoo Basin. Located in South Africa, this Permian and Triassic fossil treasure-trove is a long way away from where past evidence of a 6th mass extinction has been found - helping sell the argument that it was a global event.
Specifically, the researchers found that around 74 to 80 percent of their unearthed species became extinct along with the dinocephalians in a geologically short period of time from 272.3 to around 259.1 million years ago. Not only do these extinctions clearly predate the Great Dying, but they also coincide with the proposed 6th event.
"The South African Karoo rocks host the richest record of middle Permian land-living vertebrate animals," Day added. "This dataset, the culmination of 30 years of fossil collecting and diligent stratigraphic recording of the information, for the first time provides robust fossil and radioisotopic data to support the occurrence of this [6th] extinction event on land."
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