Recorded deep in the bedrock of Earth is a detailed history of mass specie extinction. These major die-offs span hundreds of millions of years and range from tiny microbes to the majestic lizards and birds we know today as dinosaurs.
The most recent of these occurrences was the Cretaceous-tertiary Extinction. This massive die-off took place 65 million years ago and is believed to have wiped out nearly half of all plants and animals, including all of the dinosaurs. Before that was the Triassic-jurassic Extinction which occurred roughly 210 million years ago and marked the beginning of the dinosaurs after other vertebrate land species went extinct.
The Permian-triassic Extinction happened only 30 million years before the Triassic-jurassic extinction and is considered to be the largest mass extinction in Earth's history. Some 365 million years ago the Late Devonian Extinction marked the end of many tropical marine species. And as far back as 440 million years ago, small marine organisms died out completely during the Ordovician-silurian Extinction.
Five times the Earth or the Universe nearly eradicated plant and animal life on this planet.
Or was it six times?
New evidence suggests that there was a much earlier mass extinction than previously thought. This new evidence says that a mass die-off of single-cell organisms may have occurred two billion years ago. That's 1.56 billion years before our current, earliest recorded extinction.
The new analysis also suggests that this massive extinction was much larger than any other known die-off, much larger even, than when the dinosaurs met their fate.
"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," says geologist Malcolm Hodgskiss from Stanford University.
Researchers accredit this mass extinction to what is called the Great Oxygenation Event. According to research, Earth was of course much different. There were no animals or shrubs or insects, in fact, there was very little life on land at all. However, life in the oceans was thriving.
The organisms that could be found there were of the anaerobic kind, meaning they metabolized their food without the use of oxygen.
Seeing as oxygen was the same as poison, life was good for the anaerobic organisms; Earth's atmosphere had very little oxygen, as did the seas. That is until the cyanobacteria showed up, or blue-green algae, and literally poisoned the planet.
Cyanobacteria are photosynthetic, which means they convert sunlight into energy and expel oxygen. As the new inhabitants of Earth flourished, the previously dominant organisms were forced to places with little to no oxygen, the survivors were on the run, exiled if you will, to places like the bottom of the sea.
Through a chemical reaction of methane, oxygen, and CO2, cyanobacteria directly caused the Earth to cool and essentially sent the planet into its first Ice Age, and seemingly triggered what we know as life today.
