Increase in the atmospheric oxygen led to the development of microbe metabolism.
Explanation:
Earth's initial air and seas were without free oxygen, despite the fact that small cyanobacteria were delivering the gas as a side-effect of photosynthesis. At that point, about 2.4 billion years back, oxygen in the climate unexpectedly expanded by around multiple times in only 200 million years.
Atmospheric oxygen resulted from a change to a microbe's metabolism that evolved once, at a specific time in the earth's history
