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VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies

9. Gaia Alive: A Bio-Ecosphere Sustains Itself

Lovelock, James. Healing Gaia. New York: Harmony Books, 1991. An illustrated exposition of a “planetary medicine” which is now imperative to cope with the perilous human impact on earth’s life support systems.

Lovelock, James. The Living Earth. Nature. 426/769, 2003. A recent summary of the Gaia hypothesis whereby organisms and their environment co-evolve so as to maintain the biosphere as a single, self-regulating system.

Luhr, James, editor-in-chief. Earth. New York: DK Publishing, 2003. This profusely illustrated encyclopedia is a great resource for the evolution, structure, dynamics and composition of our home planet in its cosmic setting.

Margulis, Lynn. Symbiotic Planet: A New Look at Evolution. Reading, MA: Perseus Books, 2000. The biological process of symbiosis, especially in the bacterial realm, serves the maintenance of an organically unified biosphere.

The sum of planetary life, Gaia, displays a physiology that we recognize as environmental regulation. Gaia itself is not an organism directly selected among many. It is an emergent property of interaction among organisms, the spherical planet on which they reside, and an energy source the sun. (119)

Margulis, Lynn, et al, eds. Environmental Evolution. Cambridge: MIT Press, 2000. A survey of atmospheric, biological, and geological conditions from their Archean origins to the industrial revolution and its consequences.

Maruyama, Shigenori and Toshikazu Ebisuzaki. Origin of the Earth: A Proposal of New Model called ABEL. Geoscience Frontiers. 8/253, 2017. In this online journal from the China University of Geosciences, in a Frontiers in Early Earth History and Primordial Life issue, Earth-Life Science Institute, and RIKEN Computational Astrophysics, Japan researchers consider at length with graphic displays, via a novel theory ABEL: Advent of Bio-Elements Bombardment, how our home planet might have come to be a habitable abode for metabolic evolution. A primal phase of biochemical arrivals is later seen to promote conducive plate tectonics. See also Tandem Planet Formation for Solar System-like Planetary Systems and Subduction of the Primordial Crust into the Deep Mantle.

Nicholson, Arwen, et al. Alternative Mechanisms for Gaia. Journal of Theoretical Biology. Online August, 2018. As discussions and arguments ever persist about an evolutionary self-regulation of biospheric viability, University of Exeter Earth system scientists including Timothy Lenton, along with University of Lincoln life scientist David Wilkinson finesse a way that selective effects on a global scale may be seen to serve life’s evident long term stable presence. See also Is Gaia Alive? The Future of a Symbiotic Planet by Roberto Cazzolla Gatti in Futures (Online August 2018).

A long-standing objection to the Gaia hypothesis has been a perceived lack of plausible mechanisms by which life on Earth could come to regulate its abiotic environment. A null hypothesis is survival by pure chance, by which any appearance and persistence of regulation on Earth is illusory. Recent work, however, has proposed that persistence alone empowers a biosphere to acquire further persistence-enhancing properties. Here we use a simple quantitative model to show that such ‘selection by survival alone’ can indeed increase the probability that a biosphere will live on in the future, relative to a baseline of pure chance. Adding environmental feedback to this model shows either an increased or decreased survival probability depending on the initial conditions. The outstanding question remains the relative importance of each mechanism for the historical and continued persistence of life on Earth. (Abstract)

Nicholson, Arwen, et al. Gaian Bottlenecks and Planetary Habitability Maintained by Evolving Model Biospheres: The ExoGaia Model. arXiv:1803.08063. Earth systems scientists Nicholson, Hywel Williams, and Timothy Lenton, University of Exeter, and David Wilkinson University of Lincoln, UK who study globally organic processes at work (search Lenton) expand this approach as an effective way to detect life-bearing exoworlds. See also The Case for a Gaian Bottleneck: The Biology of Habitability by Aditya Chopra and Charles Lineweaver herein, along with Earth: Atmospheric Evolution of a Habitable Planet by Stephanie Olson, et al at arXiv:1803.05967 for similar reviews. For a later verification see Typical Climate Perturbations Unlikely to Disrupt Gaia Hypothesis by Olivia Alcabes, et al. at arXiv:1906.01112 which finds that astrogeological impacts would likely not disrupt this long term bioregulation process.

Planet habitability models traditionally focus on abiotic processes and neglect a biotic response to changing conditions on an inhabited planet. The Gaia hypothesis postulates that life influences the Earth's feedback mechanisms to form a self-regulating system, and hence that life can maintain habitable conditions on its host planet. We present the ExoGaia model - a model of simple 'planets' host to evolving microbial biospheres. Model planets orbit a 'star' which provides incoming radiation, and atmospheric chemicals have either an albedo, or a heat-trapping property. Planetary temperatures can therefore be altered by microbes via their metabolisms. We find five distinct classes of model planets, including clear examples of 'Gaian bottlenecks' - a phenomenon whereby life either rapidly goes extinct leaving an inhospitable planet, or survives indefinitely maintaining planetary habitability. These results suggest that life might play a crucial role in determining the long-term habitability of planets. (Abstract excerpts)

Noffke, Nora. Geobiology: A Holistic Scientific Discipline. Palaeogeography, Palaeoclimatology, Palaeoecology. 219/1-3, 2005. This field is coalescing to expand earth system sciences into these domains: (i) to understand environmental problems of global scale, and to predict unforeseen damages in the future, (ii) to reconstruct the history of our planet, analyzing causes and consequences of life-environment interactions during the joint evolution of life and Earth, and (iii) to explore extraterrestrial worlds by studying analogue environments on Earth. The special issue provides a dozen contributions which discuss research efforts across this array of concerns.

Ord, Alison, et al, eds. Patterns in our Planet: Defining New Concepts for the Applications of Multi-scale Non-equilibrium Thermodynamics to Earth-system Science. Philosophical Transactions of the Royal Society A. 368/3, 2010. An Introduction to a special issue on topics such as self-organized criticality in earthquake dynamics, geophysical flows, and a coupled biosphere-climate model. Yet despairing 2010 books by Carroll, Impey, and Gleiser over a 19th century entropic arrow of time do not even mention this robust 21st century science of an animate universe that could just as well be seen as spontaneously winding itself up in a way we are just beginning to fathom.

Although non-equilibrium thermodynamics began to grow in the 1930s (Onsager 1931; Prigogine 1955; Truesdell 1969), it has had something of a resurgence in the physical sciences in recent years, embracing ideas from classical solid mechanics and stimulated by advances in computer performance. Non-equilibrium thermodynamics has now advanced to a stage where it is beginning to offer a unifying approach to understanding and modelling coupled phenomena and complex systems as a whole. (3)

Palmer, Douglas. Prehistoric Past Revealed: The Four Billion Year History of Life on Earth. Berkeley: University of California Press, 2003. A popular survey of the geological and evolutionary course of our home planet. The book is of interest because it works back from recent Ice Age times to the origins of life and the earth in the same sequence that it was found and reconstructed by humankind.

Payne, Jonathan, et al. The Evolution of Complex Life and the Stabilization of the Earth System. Interface Focus. June, 2020. For an issue on The Origin and Rise of Complex Life, Stanford, Tufts, Yale, and University of Hawaii biogeologists advance understandings of planetary bioregulations as they long proceeded to modify and tailor environmental conditions to organismic life’s advantage.

Earth's increasing habitability could result from: (i) a decrease in the intensity of interactions among species; (ii) a decrease in the prevalence or intensity of geological triggers; (iii) a decrease in the sensitivity of animals to environmental disturbance; or (iv) an increase in the strength of stabilizing feedbacks within the climate system and biogeochemical cycles. There is evidence from palaeontology, geochemistry and comparative physiology that animals have become more resilient to an environmental change and that the evolution of complex life has, on the whole, strengthened stabilizing feedbacks in the climate system. The differential success of certain phyla and classes appears to result from anatomical solutions to the evolution of macroscopic size that arrived during Ediacaran and Cambrian time. (Abstract excerpt)

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