Before the Great Oxygenation Event only unicellular life was possible. After the event, more complex life could be introduced. Also, the extra oxygen in Earth’s atmosphere meant that the great oxygen sinks on and in Earth (the crust and the mantle) could be filled up. This ample supply paved the way for the Second Great Oxygenation Event and the possibility for large, active animals. Unless the First Great Oxygenation Event had occurred as early as it did in Earth’s history, human life would never have been possible on Earth.
Recently, a team of British environmental scientists discovered how Earth transitioned from a low atmospheric oxygen state to a high one and how it did so as early and as quickly as it did. The team determined that a certain minimum level of oxygen in Earth’s atmosphere will trigger the development of effective ultraviolet shielding in the troposphere through the formation of ozone. That shielding not only permits more efficient photosynthesis to occur, but it also gives oxygen molecules in the troposphere a longer lifetime. These effects result in a large and rapid boost in the oxygen content of the atmosphere.
The development of these conclusions is where the research of the British team stops. What they overlooked is that the trigger will not be “pulled” unless considerable supernatural intervention occurs. For the trigger to be pulled early enough and effectively enough that human life becomes an eventual possibility, photosynthetic life must be introduced on Earth at the earliest possible moment; that is, immediately after the late heavy bombardment event ends (date = 3.8 billion years ago). This early photosynthetic life must be both abundant and ubiquitous throughout the Earth. For the abundance and ubiquity to be possible, there must be many diverse species of photosynthetic life. Furthermore, photosynthetic life must remain abundant, ubiquitous, and diverse continuously for many hundreds of millions of years. Such life, therefore, either must be hardy enough to survive the many life-disturbing events occurring during Earth’s early history and/or the Creator must be aggressively re-creating life during this era (see Psalm 104:27-30).
Thanks to the many supernatural interventions on the part of the Creator, all these conditions were met and the Great Oxygenation Event did indeed occur.