NASA picture of oxygen levels in our atmosphere. (NASA)

Oxygen Jinx in Air Started Animal Life to Begin With, Says New Study

We’re all familiar that oxygen is the driver of life. However, a new study has shown that a tiny jinx of oxygen was what started animal evolution on earth.

Scientists from various institutes formed a research team and analyzed the long-known theory that a drastic alteration in oxygen levels might have triggered the formation of complex forms of life on earth like sharks, squids and whales from less complex forms of life like algae, sponges and microorganisms.

The research team discovered although oxygen levels increased in the atmosphere and water it was at lower levels than what was believed to be necessary to provoke life changes. For the study, the team guesstimated oxygen levels by evaluating iron obtained from shale rock that once used to be mud on olden seafloors. The position and quantity of iron in the rock provided significant hints about the chemistry of old ocean water over time.

The rock data was assembled from around the world by the research team and then evaluated, accumulated, and statistically modeled. Benjamin Gill who is the assistant professor of geoscience in the Virginia Tech’s College of Science and one of the members of the research team suggested that nearly 635 million to 542 million years before, “the Earth passed some low, but critical, threshold in oxygenation for animals.”

He added that the “threshold was in the range of a 10 to 40 percent increase,” and marked the second time when earth saw its oxygen levels noticeably rise, in its entire history. Several organisms on planet earth, along with animals, require oxygen to foster energy and carry out other functions of life.

Erik Sperling who is the assistant professor of geological and environmental sciences at Stanford University as well as the first author of the study said that in the future as part of this research they require “much more precise constraints on the magnitude of oxygenation on Cambrian animal life.” The study has been published in the journal Nature.

Oxygen currently accounts for about 21 percent of the gases in the planet’s atmosphere, but that level hasn’t been steady over Earth’s history, according to previous studies.

It was believed that for the first couple of billion years, there was little oxygen in the atmosphere and about 2.5 billion years ago, oxygen started getting added to the atmosphere by photosynthetic cyanobacteria. “Oxygen is produced as a waste product of photosynthesis. It is consumed through respiration,” said University of Michigan climate scientist Chris Poulsen, lead author of a study published in Science earlier.

That waste product sparked a mass extinction known as the Great Oxygenation Event but new forms of life evolved using oxygen in respiration, and atmospheric oxygen levels continued to increase. Atmospheric oxygen levels have varied from a low of 10 percent to a high of 35 percent over the last 540 million years, said Poulsen.

Poulsen and his colleagues were studying the climate and plants of the late Paleozoic, modifying a climate model to test the oxygen idea, with results showing that changes in oxygen concentration did indeed have an impac.

“Oxygen levels are dropping today but at a very slow rate, approximately tens of parts per million per year,” he says. “This rate is much too slow to affect climate in the modern world.” Give the planet another million years, though, and future climate scientists will need to add oxygen to their models to get the full picture.


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