Fig. 2: Summary of current understanding and intervals of time for future research.
From: Future directions for understanding the coevolution of life and oxygen

A Reported intervals of high priority according to experts (n = 37). Highest reported interval of priority occurs during the mid-late Tonian 800–720 Ma (timescale overlap of 14 individual responses). B Atmospheric oxygen throughout Earth history2. C Global carbon isotope record based on a preliminary compilation72.