BioSystems 188 (2020) 104063 Contents lists available at ScienceDirect BioSystems journal homepage: www.elsevier.com/locate/biosystems Review article Contrasting theories of life: Historical context, current theories. In search of an ideal theory Athel Cornish-Bowden <, María Luz Cárdenas Aix Marseille Univ, CNRS, BIP, IMM, Marseille, France ARTICLEINFO ABSTRACT Keywords: Most attempts to define life have concentrated on individual theories, mentioning others hardly at all, but here Autocatalytic sets we compare all of the major current theories. We begin by asking how we know that an entity is alive, and Autopoiesis continue by describing the contributions of La Mettrie, Burke, Leduc, Herrera, Bahadur, D'Arcy Thompson and, Chemoton especially, Schrödinger, whose book What is Life? is a vital starting point. We then briefly describe and discuss Closure (M, R) systems, the hypercycle, the chemoton, autopoiesis and autocatalytic sets. All of these incorporate the Hypercycle Metabolic circularity idea of circularity to some extent, but all of them fail to take account of mechanisms of metabolic regulation, (M, R) systems which we regard as crucial if an organism is to avoid collapsing into a mass of unregulated reactions. In Origin of life a final section we study the extent to which each of the current theories can aid in the search for a more Self-organization complete theory of life, and explain the characteristics of metabolic control analysis that make it essential for an adequate understanding of organisms. Contents 1. General introduction .......................................................................................................................................................................................... 3 1.1. Definitions of life ................................................................................................................................................................................... 3 1.2. The living state ...................................................................................................................................................................................... 3 1.3. Why does it matter? ............................................................................................................................................................................... 5 1.4. Origin of life.......................................................................................................................................................................................... 6 1.5. La Mettrie (1748): Man a Machine ........................................................................................................................................................... 6 1.6. Obsolete theories.................................................................................................................................................................................... 6 1.6.1. Vitalism................................................................................................................................................................................... 7 1.6.2. Spontaneous generation ............................................................................................................................................................ 7 1.6.3. Creationism ............................................................................................................................................................................. 7 1.7. Final cause ............................................................................................................................................................................................ 8 1.8. Nineteenth century ................................................................................................................................................................................. 8 1.9. Creating lifelike particles ........................................................................................................................................................................ 9 1.9.1. John Burke (1906) ................................................................................................................................................................... 9 1.9.2. Stéphane Leduc (1910, 1912).................................................................................................................................................... 9 1.9.3. Alfonso Herrera (1904, 1924).................................................................................................................................................... 9 1.9.4. Krishna Bahadur (1950s) .......................................................................................................................................................... 10 1.10. Physical and mechanical constraints ........................................................................................................................................................ 10 1.11. Erwin Schrödinger (1944) ....................................................................................................................................................................... 10 1.11.1. Negative entropy, codescript ..................................................................................................................................................... 10 1.11.2. Biology and the laws of physics................................................................................................................................................. 11 1.12. Theories of life and molecular biology ..................................................................................................................................................... 12 1.13. Is it possible to define ``life''? .................................................................................................................................................................. 12 2. Current theories of life ....................................................................................................................................................................................... 12 2.1. General points........................................................................................................................................................................................ 12 2.1.1. Closure.................................................................................................................................................................................... 12 2.1.2. Lack of communication between authors.................................................................................................................................... 14 < Corresponding author. E-mail addresses: [email protected], [email protected] (A. Cornish-Bowden), [email protected], [email protected] (M.L. Cárdenas). https://doi.org/10.1016/j.biosystems.2019.104063 Received 4 June 2019; Received in revised form 10 October 2019; Accepted 10 October 2019 Available online 9 November 2019 0303-2647/' 2019 Published by Elsevier B.V. A. Cornish-Bowden and M.L. Cárdenas BioSystems 188 (2020) 104063 2.2. (M, R) systems (1958 onwards) ............................................................................................................................................................... 15 2.2.1. Infinite regress ......................................................................................................................................................................... 15 2.2.2. Closure to efficient causation .................................................................................................................................................... 15 2.2.3. Modelling and simulation.......................................................................................................................................................... 16 2.2.4. Membranes and barriers ........................................................................................................................................................... 17 2.2.5. Enzymes and metabolites .......................................................................................................................................................... 17 2.2.6. Anticipatory systems................................................................................................................................................................. 18 2.3. The hypercycle (1971 onwards)............................................................................................................................................................... 18 2.3.1. Eigen's (Woese's) paradox ......................................................................................................................................................... 19 2.3.2. The RNA world ........................................................................................................................................................................ 19 2.3.3. The hypercycle......................................................................................................................................................................... 20 2.3.4. Quasi-species ..........................................................................................................................................................................