03/2 Planet Earth 2 | Gaia Hypothesis.pdf
Conclusion
1. Life on Earth implies life elsewhere, but it is not seen as the ‘Fermi Paradox’: Rare Earth and Anthropic Principle arguments possibly apply
2. A counter argument is the Mediocrity Principle and the Gaia Hypothesis proposes a novel homeostatic geophysiology making life possible
3. A chemical disequilibrium of Earth’s atmosphere is the key Gaia concept as perceived by Lovelock from work on Mars life detection probes
4. Lovelock’s GMST 20˚C prognostication shows Gaia in action with a homeostatic suppression of human impacts to protect its physiology
AR Research and Opinion
Discussion
Science is obliged to find empirical explanations according to the scientific method: a ‘God’s wot did it’ approach cannot apply. Life on Planet Earth is yet to be matched by life elsewhere. It is possible to conjecture a large number of extant extraterrestrial civilisations in the universe, but they are not apparent in human history or currently observable. ‘Where are they?’ is the Fermi Paradox. The Rare Earth argument and the Anthropic Principle that observations of the universe must involve an observer would go towards explaining the Paradox, which had been raised before Fermi. However, the counter argument is the Mediocrity Principle that if an item is drawn at random from one of several sets or categories, it is more probable to come from the most numerous category than from any one of the less numerous categories. In this puzzle of life on Earth, the Lovelock + Margulis Gaia Hypothesis has been an important advance as a rational totalisation consistent with the scientific method. However, the Popper falsifiability criterion presents problems: it is a hypothesis not a theory. Lovelock’s work on Mars life detection probes led him to see an atmosphere in chemical disequilibrium as a sign of life. The Great Oxygenation Event of prokaryote and later eukaryote photosynthesis leads from an anaerobic chemical equilibrium to an aerobic chemical disequilibrium with trace levels of CO2 and CH4 as an emergent property of the biosphere given Carbon Sequestration. CO2 and H2O are available to be reduced by photosynthesis to carbohydrate food releasing O2 into the atmosphere with a solar energy capture for metabolic activity at a current 1.3 x 10
AR Research and Opinion
Chronology
2.3bn BP |
Great Oxygenation Event occurs: cyanobacteria produce an O2 atmosphere by photosynthesis oxidising CH4 causing Huronian Ice Age mass extinction of anaerobic life |
2.1bn BP |
Intense selective environmental pressure favours the symbiogenesis of primitive eukaryotes with nucleus envelopes resistant to O2 with meiosis and sexual reproduction |
1924 |
Kozo-Polyansky publishes Symbiogenesis A New Principle of Evolution: symbiogenesis is the species innovator and Darwin’s natural selection is the species eliminator |
1965 |
Lovelock working on life detection probes for Mars conjectures an Earth superorganism concept proposing an atmospheric chemical disequilibrium being a life indicator |
1967 |
Margulis publishes On Mitosing Cells: prokaryote endosymbiosis is the origin of nucleated eukaryote cells as had been conjectured, but then was technically unconfirmable |
1974 |
Lovelock and Margulis publish Homeostatic tendencies: the ‘Gaia Hypothesis’ that the atmospheric chemical disequilibrium observed is a biosphere emergent property |
2000 |
Ward et al publish Rare Earth: exoplanets have life only if demanding criteria are met and life would mainly be prokaryotic and only briefly complex multicellular eukaryotic |
2009 (i) |
Ward publishes The Medea Hypothesis: excepting the K-Pg event, mass extinctions by adverse atmospheres are created by microbial life activity and so Gaia is refutable |
2009 (ii) |
Lovelock publishes The Vanishing Face of Gaia: the Gaian chemical disequilibrium is being destroyed by fossil fuel burning threatening the excess human population |
2013 |
Tyrrell publishes On Gaia: the environment and life are in a form of coevolution but without any emergent property any explanation of life lies in the weak anthropic principle |
AR Research and Opinion
Glossary
Aerobic atmosphere |
Free Oxygen O2 is present in Earth’s atmosphere |
Dry atmosphere is N2 78.1%, O2 21.0%, Ar2 0.9%, trace CO2, but wet water vapour H2O 0.4% varying with altitude |
Carbon Seq'n |
Sequestration causes a chemical disequilibrium |
Sequestered as mineral carbonates, methane clathrates and fossil fuels there is only trace atmospheric CO2 + CH4 |
Gaia Hypothesis |
Mother Earth γαία Earth goddess of Greek myth |
Hypothesis that the biotic and abiotic have interacted to produce the emergent property of a homeostatic system |
Great Oxygenation |
Event Biotic O2 fills sinks and surplus O2 appears |
Photosynthesising prokaryotes and later eukaryotes reduce CO2 + H2O to carbohydrates for food releasing O2 |
Kozo-Polyansky |
Boris 1890 – 1957 An evolutionary biologist |
Kropotkin mutualism and Mereschowski symbiogenesis led him to proposing an endosymbiont eukaryote origin |
Macroevolution |
Punctuated evolution at the species level |
Macro versus micro taken to be a time difference but also a genomic path difference: saltational genomic change |
Margulis |
Lynn Petra 1938 – 2011 With Lovelock proposes Gaia |
She gave a greater weight to Russian mutualism than to English competition making endosymbiosis an orthodoxy |
Medea Hypothesis |
Murdering Mother μήδεια of Greek myth |
Gaia Hypothesis coevolution having emergent properties is refuted: a human control of the CO2 level is required |
Microevolution |
Phyletic gradualism within the species level |
Micro versus macro taken to be a time difference but also a genomic path difference: gradual mutational change |
Symbiogenesis |
Evolutionary theory of horizontal transmission |
Gene and organelle transfer is horizontal cell to cell this leads to macroevolution in distinction to microevolution |
AR Research and Opinion