In Mythology, Gaia is the personification of our planet, "Mother Earth". The term originates from Ancient Greece.

Scientifically, the "Gaia Hypothesis" was a long-term scientific study which proposed that "all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet."

From hypothesis to theory
"James Lovelock called his first proposal the "Gaia hypothesis", but the term established nowadays is "Gaia theory". Lovelock explains that the initial formulation was based on observation, but still lacked a scientific explanation. The Gaia Hypothesis has since been supported by a number of scientific experiments and provided a number of useful predictions, and hence is properly referred to as the Gaia theory. In fact, wider research proved the original hypothesis wrong, in the sense that it is not life alone but the whole Earth system that does the regulating.

In 2001, a thousand scientists at the European Geophysical Union meeting signed the Declaration of Amsterdam, starting with the statement 'The Earth System behaves as a single, self-regulating system with physical, chemical, biological, and human components.'

In 2005 the Ecological Society of America invited Lovelock to join their Fellowship, and in 2006 the Geological Society of London awarded Lovelock with the Wollaston Medal for his work on the Gaia theory.

Nowadays the Gaia theory is being researched further, mainly in the multidisciplinary fields of Earth system science and biogeochemistry. It is also being applied increasingly to studies of climate change."

The "Earth is alive" controversy
"The concept of a living Earth has caused a lot of controversy, partly due to the different attributes and connotations given to this hypothetical life, partly because of the straightforward language used by Lovelock in his writings.

For instance, evolutionary biologists such as the late palaeontologist Stephen Jay Gould and the ethologist Richard Dawkins attacked his statement in the first paragraph of his book (1979), that 'the quest for Gaia is an attempt to find the largest living creature on Earth.'

James Lovelock sustains that agreeing on a rational answer is not possible because science has not yet formulated a full definition of life.

A basic criterion of the empirical definition of a life-form is its birth out of natural selection and its ability to replicate and pass on its genetic information to a succeeding generation. Dawkins stressed that, consequently, an argument against the idea that Gaia as a living organism is the fact that the planet is not the offspring of any parents and is unable to reproduce.

Lovelock, however, defines life as a self-preserving, self-similar system of feedback loops like Humberto Maturana's autopoiesis; as a self-similar system, life could be a cell as well as an organ embedded into a larger organism as well as an individual in a larger inter-dependent social context. The biggest context of interacting inter-dependent living entities is the Earth.

William Irwin Thompson suggests that the Chilean biologist Humberto Maturana and James Lovelock, with the deductive definition of autopoiesis, have provided an explanation for the phenomenon of life. Reproduction becomes optional: bee swarms reproduce, while the biosphere has no need to.

Given the possibilities, the biosphere may multiply in the future by colonizing other planets, as humankind may be the primer by which Gaia will reproduce. Humanity's exploration of space, its interest in colonizing and even terraforming other planets, lends some plausibility to the idea that Gaia might in effect be able to reproduce."