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We're all luckier than we previously thought ...
Strongly suggestive (though admittedly indirect) evidence indicates the earliest microbial life on earth suffered a mass die-off event that (proportionally) makes the "Great Dying" (Permian Extinction Event) and the K-T Boundary Event (the dinosaurs' demise) pale by comparison.
FULL STORY: https://www.sciencedaily.com/releases/2019/08/190828180437.htm
Strongly suggestive (though admittedly indirect) evidence indicates the earliest microbial life on earth suffered a mass die-off event that (proportionally) makes the "Great Dying" (Permian Extinction Event) and the K-T Boundary Event (the dinosaurs' demise) pale by comparison.
Ancient die-off greater than the dinosaur extinction
When significant oxygen entered the atmosphere, ancient life multiplied. But after a few hundred million years, Earth's oxygen plummeted, resulting in a die-off likely greater than the extinction of the dinosaurs.
Clues from Canadian rocks formed billions of year ago reveal a previously unknown loss of life even greater than that of the mass extinction of the dinosaurs 65 million years ago, when Earth lost nearly three-quarters of its plant and animal species.
Rather than prowling animals, this die-off involved miniscule microorganisms that shaped the Earth's atmosphere and ultimately paved the way for those larger animals to thrive.
"This shows that even when biology on Earth is comprised entirely of microbes, you can still have what could be considered an enormous die-off event that otherwise is not recorded in the fossil record," said Malcolm Hodgskiss, co-lead author of a new study published in Proceedings of the National Academy of Sciences.
Invisible clues
Because this time period preceded complex life, researchers cannot simply dig up fossils to learn what was living 2 billion years ago. Even clues left behind in mud and rocks can be difficult to uncover and analyze.
Instead, the group turned to barite, a mineral collected from the Belcher Islands in Hudson Bay, Canada, that encapsulates a record of oxygen in the atmosphere. Those samples revealed that Earth experienced huge changes to its biosphere -- the part of the planet occupied by living organisms -- ending with an enormous drop in life approximately 2.05 billion years ago that may also be linked to declining oxygen levels. ...
FULL STORY: https://www.sciencedaily.com/releases/2019/08/190828180437.htm