title: Hidden in plain view: degeneracy in complex systems.
abstract: Degeneracy is a word with two meanings. The popular usage of the word denotes deviance and decay. In scientific discourse, degeneracy refers to the idea that different pathways can lead to the same output. In the biological sciences, the concept of degeneracy has been ignored for a few key reasons. Firstly, the word "degenerate" in popular culture has negative, emotionally powerful associations that do not inspire scientists to consider its technical meaning. Secondly, the tendency of searching for single causes of natural and social phenomena means that scientists can overlook the multi-stranded relationships between cause and effect. Thirdly, degeneracy and redundancy are often confused with each other. Degeneracy refers to dissimilar structures that are functionally similar while redundancy refers to identical structures. Degeneracy can give rise to novelty in ways that redundancy cannot. From genetic codes to immunology, vaccinology and brain development, degeneracy is a crucial part of how complex systems maintain their functional integrity. This review article discusses how the scientific concept of degeneracy was imported into genetics from physics and was later introduced to immunology and neuroscience. Using examples of degeneracy in immunology, neuroscience and linguistics, we demonstrate that degeneracy is a useful way of understanding how complex systems function. Reviewing the history and theoretical scope of degeneracy allows its usefulness to be better appreciated, its coherency to be further developed, and its application to be more quickly realized.
authors.affiliation: Woolcock Institute of Medical Research, University of Sydney, 431 Glebe Point Road, Glebe, 2037 NSW, Australia. Electronic address: paul.mason@woolcock.org.au.
authors.forename: P H
authors.initials: PH
authors.lastname: Mason
authors.affiliation: Experimental Neuropsychology Research Unit, School of Psychological Sciences, Monash University, Australia.
authors.forename: J F
authors.initials: JF
authors.lastname: Domínguez D
authors.affiliation: Cognitive and Information Sciences, University of California, Merced 5200 North Lake Rd., Merced, CA 95343, USA.
authors.forename: B
authors.initials: B
authors.lastname: Winter
authors.affiliation: Section and Museum of History of Medicine, University of Rome "La Sapienza", viale dell'Università, 34a 00185 Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Grignolio
mesh_terms: D000486:Allergy and Immunology / Q000266:history*; D005823:Genetics / Q000266:history*; D049673:History, 20th Century; D049674:History, 21st Century; D008962:Models, Theoretical; D055585:Physical Phenomena; D009626:Terminology as Topic
keywords: Brain; Complex systems; Degeneracy; Immune system; Language; Pluripotentiality; Redundancy