Earth system

The Earth is a self-regulating system according to Gaia theory and its more mainstream offshoot, Earth system science. Through various cycles and processes, living beings around the planet cooperate to stabilize the Earth's temperature, acidity, salinity, atmosphere, and more. Thus, the Earth does not function as a hierarchy or as a competitive struggle between all beings. Rather, members of a highly decentralized global network cooperate to ensure mutual survival over millions and millions of years.

James Lovelock and Lynn Margulis first advanced the Gaia hypothesis, jointly publishing in Carl Sagan's journal Icarus. At first, they characterized the Earth as a living superorganism, drawing harsh criticism from reductionist scientists such as Richard Dawkins, who denounced the notion as "teleological." The critics asserted that the Earth cannot self-regulate since the it does not have the consciousness necessary to plan and have foresight. Lovelock responded by programming a computer simulation called Daisyworld. In Daisyworld, sunlight-reflecting white daisies and sunlight-absorbing black daisies cooperated to stabilize the planet's temperature, allowing life to thrive for an extended period of time. The model demonstrated that planetary self-regulation does not require the foresight or conscious planning.

Today, the mainstream body of research called Earth system science draws heavily on Gaian ideas but, in an effort to fit into dominant scientific culture, removes the reference to the Greek goddess Gaia. In Amsterdam in 2001, over a thousand delegates signed a statement, “The Earth System behaves as a single, self-regulating system comprised of physical, chemical, biological and human components.”

Archean

With each eon lasting a thousand million years, the Archean is the era from Earth's assembly 4.5 eons ago to the oxygen revolution 2.5 eons ago. During the Archean, Gaia theory suggests that life adapted the Earth to make it a home. There emerged a self-regulating interaction between early photosynthesizers (cyanoacteria) who cooled the Earth by removing heat-trapping carbon-dioxide from the atmosphere and methanogen decomposers (bacteria) who warmed the Earth by converting bacteria into the greenhouse gases carbon dioxide and methane. So, the photosynthesizers were like the light daisies, and the decomposers were like the dark daisies.

Proterozoic

Around 2.5 eons ago, photosynthesizers transformed the atmosphere from being methane-dominated to being oxygen-dominated. This transformation heralded a new geological era, the Proterozoic, and it allowed the evolution of new kinds of life, including the evolution of eukaryotes.

A key self-regulatory mechanism of the Proterozoic involved the deposit of calcium carbonate on the oceanic floor. Through such deposits, bacteria converted toxic soluble calcium into insoluble calcium. Although calcium is essential for many life forms, too much of it is deadly, and this self-regulatory mechanism would have been crucial for many beings' survival.

Another example of self-regulation involved salt-regulation. Few organisms can survive with an abundance of salt, and somehow oceans stayed within a safe salinity level. Various chemical reactions helped remove salt from the sea floor, and microorganisms deposited salt as sediments and as limestone.