Evolution of Atmospheric O₂ Through the Phanerozoic, Revisited

An oxygen-rich atmosphere is essential for complex animals. The early Earth had an anoxic atmosphere, and understanding the rise maintenance of high O 2 levels critical investigating what drove our own evolution assessing likely habitability exoplanets. A growing number techniques aim to reproduce changes in over Phanerozoic Eon (the past 539 million years). We assess these methods attempt draw reliable together form a consensus curve. conclude that probably made up around 5–10% during Cambrian rose pulses ∼15–20% Devonian, reaching further peak greater than 25% Permo-Carboniferous before declining toward present day. Evolutionary radiations Ordovician appear consistent with oxygen driver, Devonian “Age Fishes” coincides rising above 15% atm. ▪ animals such as humans. review reconstructing variation years Eon). produce plot most atmospheric levels. Cambrian, Ordovician, periods may be linked rises concentration.