The Gaia hypothesis states that the earth and its biosphere can be viewed as one living being, since the biosphere (the entirety of all organisms) creates and maintains conditions that enable not only life but also the evolution of more complex organisms. The earth's surface forms a dynamic system that stabilizes the entire biosphere. This hypothesis presupposes a certain definition of life , according to which living beings are characterized in particular by the ability to organize themselves.
The Gaia Hypothesis was developed by the microbiologist Lynn Margulis and the chemist, biophysicist, and physician James Lovelock in the mid-1970s.
The name is derived from Gaia , the great mother in Greek mythology . The Gaia hypothesis, for its part, motivated fields of activity such as geophysiology , which places landscape ecology in a holistic context.
Empirical basis for the Gaia hypothesis
In their books, the founders of the Gaia hypothesis put together various facts that are supposed to support the image of the self-organizing, "living" planet. More recent geoscientific findings have further fueled the discussion.
Molecular oxygen is a highly reactive substance that quickly bonds with other elements and thus disappears. Iron rusts, wood burns. The astonishing thing is that the oxygen content of the atmosphere is constant: No matter how much iron rusts and how much wood burns, the global oxygen content remains unchanged. This becomes particularly exciting when one takes into account that “fossil air” from ice cores or amber has a very similar, often the same, composition as today's. Obviously, since life in the country has been active, the oxygen content of the air has changed little. The Gaia hypothesis states that the system "life" itself keeps the proportion stable. (A consequence of this consideration is that another planet with an atmosphere that contains oxygen and a gas that reacts with oxygen must harbor life - so far none has been discovered. The atmosphere of Jupiter's moon Europa contains oxygen, but not significantly other substances .)
Example of climate fluctuations
There is increasing evidence that up to 600 million years ago the climate was exposed to extreme fluctuations that have not existed since then. At times the earth was literally covered by an ice sheet (" snowball earth "), while at other times it was completely free of ice. Critics of the Gaia hypothesis therefore argue that such extreme fluctuations contradict the idea of a balanced earth.
Proponents see it the other way round: One explanation for these early climatic fluctuations is that in that early period ( Precambrian ) there were no complex organisms with skeletons or calcareous shells. Because the calcareous marine plankton plays an enormous role for the CO 2 balance of the oceans today . When these organisms grow, they take up carbon dioxide (CO 2 ) from the water, and when they die again they sink to the sea floor with their calcareous shell, where massive calcareous sediments then form over the course of millions of years. In this way, the CO 2 content of the oceans is chemically stabilized - indirectly also that of the atmosphere. The emergence of these organisms would therefore have helped to stabilize and thus improve the living conditions on earth.
Example salinity of the seas
The salt content of the oceans is constant at 3.5%. Although considerable amounts of minerals continue to be released from the land and transported into the sea, the salt content has not increased for millions of years. If one assumes that the mineral load in earlier times was as high as it is today, there must now be so much salt in the oceans that higher forms of life could no longer exist. In fact, there are processes that remove salt from the ocean. This includes, on the one hand, the formation of lagoons and enclosed sea basins, in which sea water collects, evaporates and in this way powerful salt deposits form. Reef-building organisms are involved in the formation of such lagoons. According to Lovelock, this is also a process in which the community of living beings itself ensures that their living conditions are maintained. Second, methyl chloride and methyl iodide are produced by seaweed and then released into the atmosphere. This biological process also removes salt components such as chlorine from the seawater.
Recent research speaks against some of these arguments. The theory that the primordial ocean had become increasingly salty over time could not be confirmed. Apparently the salinity was higher than it is today over a billion years ago - which could have been one of the reasons why it took so long for higher life forms to develop in the oceans.
The origins of the Gaia hypothesis lie in the scientific background of the two researchers James Lovelock and Lynn Margulis. The geochemist Lovelock dealt intensively with how the biosphere has and is still changing the earth's atmosphere over the course of the earth's history . In 1969 he postulated a feedback mechanism for a tendency to decrease in the concentration of the greenhouse gas CO 2 with increasing solar radiation. "These phenomena," wrote Lovelock, "can only be understood if the planet is viewed as a single living organism."
The biologist Lynn Margulis, on the other hand, is considered to be one of the founders of the endosymbiotic theory , according to which today's cells once emerged from the symbiosis of independent organisms. The idea of symbiosis has shaped her entire biological thinking. "Gaia", said Greg Hinkle (student of Lynn Margulis and now a professor), was "symbiosis viewed from space". After all, the Gaia hypothesis says that the totality of the organisms on earth form a larger organism in symbiosis, so to speak.
The name Gaia Hypothesis is based on a suggestion by the writer William Golding , who lived in the same village as (until 1976) Lovelock ( Bowerchalke , Wiltshire , UK). Golding's proposal was based on Gea, an alternative spelling for the name of the Greek goddess used as a prefix in geology, geophysics and geochemistry. Golding addressed Gaia Mater in his 1983 Nobel Prize speech.
In 1983 Glenn Shaw proposed an alternative, later known as the CLAW hypothesis , according to which the global thermostat is not based on the carbon cycle between the biosphere and subducted sediments, but on a sulfur cycle between the ocean and the atmosphere. Also plays phytoplankton a major role.
Several scientific symposia have dealt with the Gaia theory, the most recent of which was held in Arlington in 2006 . Some scientists (above all Peter Ward ) have now formulated a counter-thesis in which they describe the biosphere more as Medea , since in certain cases it can also be self-destructive. As evidence, they cite, among other things, recent findings according to which halogen hydrocarbons produced by bacteria could have triggered the mass extinction at the Permian-Triassic border .
Understanding of life
The Gaia hypothesis is based on a systems- theoretical understanding of life. A living being is therefore an open and entropy- producing system that can reactively and self-organizingly adapt to its environment in such a way that it is able to keep its entropy dynamically below its maximum entropy by exporting entropy. Another central characteristic of living beings is reproduction .
In order to underpin the Gaia hypothesis and to counter the criticism that it is purely teleological , Lovelock created Daisyworld, a simple computer simulation in which life in a self-regulating process maintains constant environmental conditions on a planet despite changing external parameters.
Effect and spiritual transfiguration
Since its formulation, the hypothesis has been in the discussion between criticism and fascination for the image it transports.
The founder of the Gaia Hypothesis, James Lovelock, comments:
- “When I speak of a living planet, I shouldn't have any animistic overtones; I am not thinking of a sentient earth or of stones that move according to their own will and purpose. I think of everything the earth might do, such as climate control, as automatic, not as an act of will; above all, I think of none of it as happening outside the strict limits of the natural sciences. I respect the attitudes of those who find solace in the church and say their prayers, but at the same time admit that logic alone does not provide convincing grounds for believing in God. In the same way I respect the attitudes of those who find solace in nature and perhaps want to say their prayers to Gaia. "
In the course of the ecology movement , the Gaia hypothesis has found many supporters in the hippie and New Age movements. Here the earth is occasionally represented as an "animated" organism that - like an earth goddess - punishes and rewards. This gives processes of an ecosystem a meaning that leads to teleological attempts at explanation. The founders of the hypothesis have always distanced themselves from such an interpretation of their hypothesis.
The Gaia hypothesis is presented in the movie Kingsman: The Secret Service as a research area of the fictional scientist Professor James Arnold.
- Nadja Podbregar: Organism Earth? From the Gaia hypothesis to the system earth In: Nadja Podbregar; Dieter Lohmann: In focus: geological knowledge. How does our planet work? Springer Verlag, Berlin, Heidelberg, 2013, e- ISBN 978-3-642-34791-7 , pp. 153-160.
- Helan Jaworski: Le Géon ou la Terre vivante . Librairie Gallimard, Paris 1928.
- Jim E. Lovelock: Our Earth Will Survive: GAIA, An Optimistic Ecology. (From the English by Constanze Ifantis-Hemm.) Piper, Munich 1982, ISBN 3-492-02580-3 ; Original: James Lovelock: Gaia - a new look at life on Earth ; 1979
- James Lovelock: The Gaia Principle: The Biography of Our Planet. (Translated from the English by Peter Gillhofer and Barbara Müller.) Artemis & Winkler, Zurich, Munich 1991. Ill., Graphic representation; ISBN 3-7608-1050-0 , original: The ages of Gaia
- James Lovelock: Gaia: The earth is a living being. (Translated from the English by Jochen Eggert and Marcus Würmli.) Scherz, Bern, Munich, Vienna 1992. 191 p .; Ill., Graph. Darst .; ISBN 3-502-17420-2 ; Original: GAIA - The practical science of planetary medicine
- James Lovelock: Gaia's Revenge. Why the earth is resisting. List 2007, ISBN 3-471-79550-2 .
- Lynn Margulis: Symbiotic Planet: A New Look at Evolution . Basic Books, ISBN 0-465-07272-0 .
- Lynn Margulis: The Other Evolution . 1999. ISBN 3-8274-0294-8 . (German translation)
- Elisabet Sahtouris: Gaia. Earth's past and future . Insel Verlag, Frankfurt / M. 1998, ISBN 3-458-16525-8 .
- ↑ James Lovelock, Lynn Sagan: Atmospheric homeostasis by and for the biosphere: the Gaia hypothesis In: Tellus. Series A. Stockholm: International Meteorological Institute. Vol. 26 (1-2), 1974, pp. 2-10.
- ^ L. Paul Knauth: Salinity history of the Earth's early ocean. In: nature 395 , pp. 554–555 (October 8, 1998)
- ↑ http://www.nobelprize.org/nobel_prizes/literature/laureates/1983/golding-lecture.html
- ^ Glenn E. Shaw: Bio-controlled thermostasis involving the sulfur cycle. Climate Change 5, 1983, pp. 297-303, doi: 10.1007 / BF02423524 .
- ↑ Peter Ward : Gaia's evil twin: Is life its own worst enemy? In: New Scientist No. 2713