What Does History Teach Us about the Major Transitions and Role of Disturbances in the Evolution of Life and of the Earth System?

This chapter explores the connections between the evolution of life and past changes of the Earth system. The concept of major transitions in evolution is extended beyond those associated with the storage and transmission of information to encompass those associated with the transformation of free energy and matter. A tentative synthesis of major transitions in the history of the Earth system is offered. Our review suggests that major transitions in the evolution of life are usually associated with major transitions in the global state of the environment, and that cause and effect are often difficult to disentangle. This is consistent with the notion that the Earth with abundant life is a tightly coupled feedback system (“Gaia”). It is unclear whether major transitions of life and of the planet are always associated, not least because there are a number of competing hypotheses to explain each major transition of the Earth system. External disturbances (e.g., asteroid impacts, massive volcanic eruptions) appear in some cases to have triggered significant transitions of the system between different (quasi-stable) states. However, the largest transitions in the state of the Earth system appear to have been internally generated with evolutionary innovation playing a leading role.