Neural Darwinism

Neural Darwinism is a biological, and more specifically Darwinian and selectionist, approach to understanding global brain function, originally proposed by American biologist, researcher and Nobel-Prize recipient Gerald Maurice Edelman (July 1, 1929 – May 17, 2014). Edelman's 1987 book Neural Darwinism introduced the public to the theory of neuronal group selection (TNGS), a theory that attempts to explain global brain function. TNGS (also referred to as the theory of neural Darwinism) has roots going back to Edelman and Mountcastle's 1978 book, The Mindful Brain – Cortical Organization and the Group-selective Theory of Higher Brain Function, which describes the columnar structure of the cortical groups within the neocortex, and argues for selective processes operating among degenerate primary repertoires of neuronal groups. The development of neural Darwinism was deeply influenced by work in the fields of immunology, embryology, and neuroscience, as well as Edelman's methodological commitment to the idea of selection as the unifying foundation of the biological sciences.

Introduction to neural Darwinism Neural Darwinism is really the neural part of the natural philosophical and explanatory framework Edelman employs for much of his work – Somatic selective systems. Neural Darwinism is the backdrop for a comprehensive set of biological hypotheses and theories Edelman, and his team, devised that seek to reconcile vertebrate and mammalian neural morphology, the facts of developmental and evolutionary biology, and the theory of natural selection into a detailed model of real-time neural and cognitive function that is biological in its orientation. It is built from the bottom-up utilizing the variation that shows up in nature. This is in contrast to computational and algorithmic approaches that view variation as noise in a system of logic circuits with point-to-point connectivity. The book, Neural Darwinism – The Theory of Neuronal Group Selection (1987), is the first in a trilogy of books that Edelman wrote to delineate the scope and breadth of his ideas on how a biological theory of consciousness and animal body plan evolution could be developed in a bottom-up fashion. In accordance with principles of population biology and Darwin's theory of natural selection – as opposed to the top-down algorithmic and computational approaches that dominated a nascent cognitive psychology at the time. The other two volumes are Topobiology – An Introduction to Molecular Embryology (1988) with its morpho-regulatory hypothesis of animal body plan development and evolutionary diversification via differential expression of cell surface molecules during development; and The Remembered Present – A Biological Theory of Consciousness (1989) – a novel biological approach to understanding the role and function of "consciousness" and its relation to cognition and behavioral physiology. Edelman would write four more books for the general lay public, explaining his ideas surrounding how the brain works and consciousness arises from the physical organization of the brain and body – Bright Air, Brilliant Fire – On the Matter of the Mind (1992), A Universe of Consciousness – How Matter Becomes Imagination (2000) with Giulio Tononi, Wider Than The Sky – The Phenomenal Gift of Consciousness (2004), and Second Nature – Brain Science and Human Knowledge (2006). Neural Darwinism is an exploration of biological thought and philosophy as well as fundamental science; Edelman being well-versed in the history of science, natural philosophy & medicine, as well as robotics, cybernetics, computing & artificial intelligence. In the course of laying out the case for neural Darwinism, or more properly TNGS, Edelman delineates a set of concepts for rethinking the problem of nervous system organization and function – all-the-while, demanding a rigorously scientific criteria for building the foundation of a properly Darwinian, and therefore biological, explanation of neural function, perception, cognition, and global brain function capable of supporting primary and higher-order consciousness.

Population thinking – somatic selective systems

Edelman was inspired by the successes of fellow Nobel laureate Frank MacFarlane Burnet and his clonal selection theory (CST) of acquired antigen immunity by differential amplification of pre-existing variation within the finite pool of lymphocytes in the immune system. The population of variant lymphocytes within the body mirrored the variant populations of organisms in the ecology. Pre-existing diversity is the engine of adaptation in the evolution of populations.

"It is clear from both evolutionary and immunological theory that in facing an unknown future, the fundamental requirement for successful adaptation is preexisting diversity". – Gerald M. Edelman (1978) Edelman recognizes the explanatory range of Burnet's utilization of Darwinian principles in describing the operations of the immune system - and, generalizes the process to all cell populations of the organism. He also comes to view the problem as one of recognition and memory from a biological perspective, where the distinction and preservation of self vs. non-self is vital to organismal integrity. Neural Darwinism, as TNGS, is a theory of neuronal group selection that retools the fundamental concepts of Darwin and Burnet's theoretical approach. Neural Darwinism describes the development and evolution of the mammalian brain and its functioning by extending the Darwinian paradigm into the body and nervous system.

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