The research also helps explain why the ‘Great Oxidation Event’, which introduced oxygen into the atmosphere around 2.4 billion years ago, did not generate modern levels of oxygen. 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. 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. It was only when land plants came about did we see a more significant rise in atmospheric oxygen,” Lenton said. By 470 million years ago the first plants grew on land with the first land animals such as millipedes appearing around 428 million years ago.

Source: Mint February 05, 2017 13:28 UTC