For simple life-forms, perhaps, but complex life probably requires rather special or rare circumstances. In areas of Earth low in oxygen, the life-forms there a

For simple life-forms, perhaps, but complex life probably requires rather special or rare circumstances. In areas of Earth low in oxygen, the life-forms there are similar to ediacaran fauna: slow and soft. Increases in oxygen are probably a key cause of the Cambrian explosion. Perhaps it's possible there is another high-metabolism cycle that doesn't involve much oxygen, but nobody really knows both if a pathway exists, and if evolution can "find" it in time. Any biochemists here who want to weigh in?