The oxygenation of Earth’s atmosphere that led to the explosion of animal life on the planet began earlier and took longer than previously believed, as new research from University College London has found that the process took a total of about 100 million years.
The UCL study, which was funded by the Natural Environment Research Council and published Friday in the journal Nature Communications, explained that the process was fragmented—taking place in fits and starts over a longer period of time than scientists had originally believed.
Based on their findings, lead investigator Dr. Philip Pogge von Strandmann of the UCL Earth Sciences department and his colleagues believe that animal evolution likely started as a response to increased oxygen levels instead of being the cause of that atmospheric oxygenation.
“We want to find out how the evolution of life links to the evolution of our climate. The question on how strongly life has actively modified Earth’s climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place,” Dr. von Standmann explained in a statement.
New approach culled data using selenium isoltopes
Working alongside a team of researchers from US, UK, and Danish universities, the UCL team studied rock samples to track oxygen levels between 770 and 520 million years ago. The rocks, they explained, were laid beneath the sea at different times and taken from different locations in order to compile a long-term global picture of the planet’s oxygen levels.
Dr. von Standmann’s team measured selenium isotopes in the rocks and found that it took about 100 million years for oxygen levels to increase from less than one percent of modern levels to 10 percent. This new approach gave them more data on the gradual changes in oxygen’s abundance than traditional means, and sheds new light on one of Earth’s most significant events.
“We took a new approach by using selenium isotope tracers to analyze marine shales which gave us more information about the gradual changes in oxygen levels,” the professor noted. “We were surprised to see how long it took Earth to produce oxygen and our findings dispel theories that it was a quick process caused by a change in animal behavior.”
They also found that, during the three “snowball Earth” glaciations that occurred from 580 and 716 million years ago, temperatures fell drastically before rising again, causing glaciers to melt. This released a large amount of nutrients into the ocean, which in turn produced more plankton, which buried organic carbon in seafloor sediments and caused oxygen levels to increase.
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Feature Image: Thinkstock
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