Around 390 million years ago (Devonian period), marine animals began colonizing depths previously uninhabited. New research led by scientists from Duke...
About 2.5 billion years ago, free oxygen first started to accumulate to meaningful levels in Earth’s atmosphere, setting the stage for the rise of complex...
Oxygen levels fluctuated dramatically for about 200 million years after the start of the Great Oxidation Event, with permanent atmospheric oxygenation...
