Perhaps there were several civilizations that predated that of humans. At least that’s the basic premise of Larry Niven’s short story, “The Green Marauder.” He tells of an intelligent anaerobic life form that once flourished on Earth, then died when plants began uncontrollably to release oxygen into the atmosphere. Was it the result of a scientific experiment gone awry, or evolution in action?
Perhaps there were several civilizations that predated that of humans. At least that’s the basic premise of Larry Niven’s short story, “The Green Marauder.” He tells of an intelligent anaerobic life form that once flourished on Earth, then died when plants began uncontrollably to release oxygen into the atmosphere. Was it the result of a scientific experiment gone awry, or evolution in action?
https://non-aliencreatures.fandom.com/wiki/Anaerobic_Lifeform_(The_Green_Marauder)