That’s often been suggested. Recently, some interesting evidence has turned up (the researchers estimate 1% of today’s level).
From the BBC:
The team analysed the chromium levels – a geochemical signature – of rock sediments from Australia, Canada, China, and the United States. This allowed them to understand how much oxygen would have been present.
They found a change in the chemical components of the rocks occurred about 800 million years ago, a period when oxygen levels began to rise rapidly, already documented by previous research.
Another researcher was more critical of the study and said the role of oxygen was overstated. Nicholas Butterfield of Cambridge University’s department of Earth Sciences said: “All geochemistry is drawn from marine rocks, it’s not directly measuring the atmosphere.
See, for example, Why life remained just slime for a billion years: Turns out low oxygen WAS to blame after all (?):
As the USD researchers who studied sponges showed, life forms do not universally need a lot of oxygen.
We are living on a planet where at last one bacterium “breathes” iron and another sulfur, the bdelloid rotifer dispensed with sex in favour of horizontal gene transfer, and the sea slug just incorporated its plant meals’ chlorophyll factories (chloroplasts) [Just what is going on with the slugs has been disputed.] It almost seems as if, whatever the deficiency, a life form will be found somewhere that can cope with it. But come to think of it, would any of the above-mentioned make good fossils? Maybe we just don’t know enough yet to be sure that the famously “boring billion” years was quite so boring.
Also: Animals didn’t “arise” from oxygenation, they created it, researchers say
Theory on how animals evolved challenged: Some need almost no oxygen
New study: Oxygenic photosynthesis goes back three billion years
We should organize a panel discussion with all these people.
See also: The Science Fictions series at your fingertips (origin of life)
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