The Gaia Hypothesis is the idea that the Earth's biosphere itself is a complex, conscious, self-regulating living being1. It was named by James Lovelock in the 1980s. Lovelock, born 1919, was a British scientist who specialized in atmospheric chemistry and an environmental theorist. The concept of "emergent properties" and our Human (all-too-biological) biases may mean that we are poorly equipped to understand, or perceive, life-forms such as Gaia2. After all, if all the paint daubs of a painting were sentient, they would never be able to perceive themselves as part of a greater living picture. Lovelock writes that the way many parts of the Earth's ecosystem are self-regulating and balanced is so intriguing that it seemed to behave in the same way as a single organism3.
Other in Humankind's history have approached a similar idea. For example in classical Greece there was a man called Strato, who followed on from Aristotle. In his view "the deity was identical with Nature and, like the latter, was without consciousness [...] the fact that all writers seem to take it for granted that Strato knew no god other than the whole of Nature"4 - so excepting the small matter of consciousness, the concept of the Earth-as-a-whole-being is something that occurs to our imaginations from time to time.
Emergent properties are those that appear beyond a certain scale of organisation even though they are not present in the underlying structure5,6. If you microscopically examine a painted picture of a flower, you can catalogue the physical properties of the molecules of paint without ever finding a trace of the outline of a flower: only through their pattern as a whole does form, shape and beauty emerge. In biology and physics there are many complicated features that emerge from simple rules, simple interactions, merely repeated on a large scale7. Our consciousness arises from complex neuronal activity in our brain8,9,10. Some imagine that on larger scales, entire planets might be conscious (the Gaia hypothesis), or even the entire Universe (scientific pantheism).
Perhaps Gaia acts as an ecological super-consciousness, with complex patterns in the atmosphere forming part of its chemistry-based memory and consciousness. It is certainly far-fetched but the only problem is that it is impossible to investigate such a being, so it is a theory mostly loved by daydreamers, and in reality, most texts on the Gaia Principle are in fact books on environmentalism, on complex systems and on the atmospheric feedback mechanisms which support the Earth's equilibrium.
He remains an independent scientist living in Cornwall, UK. He advised NASA in their space program, advising them on scientific ways of looking for life on Mars. The actual naming of the Gaia Hypothesis was the suggestion of novelist William Golding11 based on "the ancient Greek myth of a female divinity who represented the earth"3. This has resulted in Lovelock having a long-lasting influence on the green movement overall12.
“Although the Gaia hypothesis extends the ecological idea by applying it to the Earth as an ecosystem and offers a holistic approach to nature, Lovelock supports technology and industrialization and is an opponent of 'back to nature' mysticism and ideas such as Earth worship. His major writings include Gaia: A New Look at Life on Earth (1979) and The Ages of Gaia: A Biography of our Living Earth (1989).”
The success of the Gaia Hypothesis was aided by the scientific notion of the biosphere which was also gaining followers in the 1970s.
“It was articulated by the Church of All Worlds, an organization of radical mystics who had originally been inspired by science fiction and utopian writings, and was formed in Missouri in 1967. The moving spirit was Tim (latter Otter) Zell, who propagated his ideas through the late 1960s and early 1970s in the Church's newsletter, which grew into the periodical Green Egg. It established the identity of modern paganism as a response to a planet in crises, and its spiritual core lay in the concept of the earth as a single, divine, living organism. [...]
[It was] James Lovelock, who, in 'a flash of enlightenment' at Pasadena, California, in 1965, who came up with the idea that 'life defines and maintains the material conditions needed for its survival', and that the whole planetary ecosystem 'seemed to exhibit the behaviour of a single organism - even a living creature'. [...] It began to become widely known amongst scientists in the mid-1970s, as he teamed up with the biologist Lynn Margulis.”
"The Triumph of the Moon: A History of Modern Pagan Witchcraft" by Ronald Hutton (1999)3