In their paper, published in Nature Communications, Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon, the University of Exeter scientists explain how organic material — the dead bodies of simple lifeforms — accumulated in the earth’s sedimentary rocks. After the Great Oxidation, and once plate tectonics pushed these sediments to the surface, they reacted with oxygen in the atmosphere for the first time.
The more oxygen in the atmosphere, the faster it reacted with this organic material, creating a regulatory mechanism whereby the oxygen was consumed by the sediments at the same rate at which it was produced.
This mechanism broke down with the rise of land plants and a resultant doubling of global photosynthesis. The increasing concentration of oxygen in the atmosphere eventually overwhelmed the control on oxygen and meant it could finally rise to the levels we are used to today.
This helped animals colonise the land, leading eventually to the evolution of humankind.
The model suggests atmospheric oxygen was likely at around 10% of present day levels during the two billion years following the Great Oxidation Event, and no lower than 1% of the oxygen levels we know today. Paper. (public access) – Stuart J. Daines, Benjamin J. W. Mills, Timothy M. Lenton. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon. Nature Communications, 2017; 8: 14379 DOI: 10.1038/NCOMMS14379 More.
Reckoning in the role of decaying dead life forms is an interesting new thought.
If you want to get involved with the oxygen and evolution controversy, make some tea and check the following links as well:
See also: Early Earth oxygen debate: Will the shooting stars please rise
Researchers: Small amount of oxygen 3.8 billion years ago
Did a low oxygen level delay complex life on Earth? (October 31, 2014)
Early Earth was indeed “extremely oxygen-poor compared to today” (January 16, 2015)
Small pre-Cambrian oxygen jump kickstarted complex life
(July 24, 2015)
Oxygen Does Not Equal Life – Implications for Abiogenesis? (September 15, 2015)
Researchers: Cyanobacteria responsible for Earth’s early oxygen
(November 28, 2015)
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
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