page_title: Gaia hypothesis
section_title: Formulation of the hypothesis
hierarchical_section_title: Gaia hypothesis / History / Formulation of the hypothesis
caption_attribution_description: English: James Lovelock, scientist and author best known for the Gaia hypothesis. Photograph taken in 2005 by Bruno Comby of Association of Environmentalists For Nuclear Energy. Original at http://www.ecolo.org/lovelock/. Released under the Creative Commons Attribution-ShareAlike license versions 2.5, 2.0, and 1.0.
context_page_description: The Gaia hypothesis, also known as the Gaia theory or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet.
  The hypothesis was formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s. Lovelock named the idea after Gaia, the primordial goddess who personified the Earth in Greek mythology. In 2006, the Geological Society of London awarded Lovelock the Wollaston Medal in part for his work on the Gaia hypothesis.
  Topics related to the hypothesis include how the biosphere and the evolution of organisms affect the stability of global temperature, salinity of seawater, atmospheric oxygen levels, the maintenance of a hydrosphere of liquid water and other environmental variables that affect the habitability of Earth.
context_section_description: Lovelock started defining the idea of a self-regulating Earth controlled by the community of living organisms in September 1965, while working at the Jet Propulsion Laboratory in California on methods of detecting life on Mars.  The first paper to mention it was Planetary Atmospheres: Compositional and other Changes Associated with the Presence of Life, co-authored with C.E. Giffin. A main concept was that life could be detected in a planetary scale by the chemical composition of the atmosphere. According to the data gathered by the Pic du Midi observatory, planets like Mars or Venus had atmospheres in chemical equilibrium. This difference with the Earth atmosphere was considered to be a proof that there was no life in these planets.
  Lovelock formulated the Gaia Hypothesis in journal articles in 1972 and 1974, followed by a popularizing 1979 book Gaia: A new look at life on Earth. An article in the New Scientist of February 6, 1975, and a popular book length version of the hypothesis, published in 1979 as The Quest for Gaia, began to attract scientific and critical attention.
  Lovelock called it first the Earth feedback hypothesis, and it was a way to explain the fact that combinations of chemicals including oxygen and methane persist in stable concentrations in the atmosphere of the Earth. Lovelock suggested detecting such combinations in other planets' atmospheres as a relatively reliable and cheap way to detect life.
  Later, other relationships such as sea creatures producing sulfur and iodine in approximately the same quantities as required by land creatures emerged and helped bolster the hypothesis.
  In 1971 microbiologist Dr. Lynn Margulis joined Lovelock in the effort of fleshing out the initial hypothesis into scientifically proven concepts, contributing her knowledge about how microbes affect the atmosphere and the different layers in the surface of the planet. The American biologist had also awakened criticism from the scientific community with her advocacy of the theory on the origin of eukaryotic organelles and her contributions to the endosymbiotic theory, nowadays accepted. Margulis dedicated the last of eight chapters in her book, The Symbiotic Planet, to Gaia. However, she objected to the widespread personification of Gaia and stressed that Gaia is "not an organism", but "an emergent property of interaction among organisms". She defined Gaia as "the series of interacting ecosystems that compose a single huge ecosystem at the Earth's surface. Period". The book's most memorable "slogan" was actually quipped by a student of Margulis': "Gaia is just symbiosis as seen from space".
  James Lovelock called his first proposal the Gaia hypothesis but has also used the term Gaia theory. Lovelock states 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. 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.
caption: James Lovelock, 2005
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