Por uma teoria cibernética da evolução - pode isso, Arnaldo?

quarta-feira, julho 08, 2015

Duality of stochasticity and natural selection: a cybernetic evolution theory

By Prof. Kurt Heininger 

Corresponding Author

Prof. Kurt Heininger 

Department of Neurology, Heinrich Heine University Duesseldorf, - Germany 

Submitting Author

Prof. Kurt Heininger 

Subject Category :ECOLOGY

Keywords : Stochasticity, natural selection, cybernetics, bet-hedging, multilevel selection, Law of Requisite Variety, mean geometric fitness

How to cite the article: Heininger K. Duality of stochasticity and natural selection: a cybernetic evolution theory. WebmedCentral ECOLOGY 2015;6(2):WMC004796 

doi: 10.9754/journal.wmc.2015.004796

Copyright:This is an open-access article distributed under the terms of the Creative Commons Attribution License(CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

WebmedCentral Peer Reviewed: No

Submitted on: 22 Feb 2015 09:03:27 PM GMTPublished on: 23 Feb 2015 07:42:40 AM GMT


Orthodox Darwinism assumes that environments are stable. There is an important difference between breeding (Darwin’s role model of evolution) and evolution itself: while in breeding the final goal is preset and constant, adaptation to varying biotic and abiotic environmental conditions is a moving target and selection can be highly fluctuating. Evolution is a cybernetic process whose Black Box can be understood as learning automaton with separate input and output channels. Cybernetics requires a closed signal loop: action by the system causes some change in its environment and that change is fed to the system via information (feedback) that enables the system to change its behavior. The input signal is given by a complex biotic and abiotic environment. Natural selection is the output/outcome of the learning automaton.

Environments are stochastic. Particularly, density- and frequency-dependent coevolutionary interactions generate chaotic and unpredictable dynamics. Stochastic environments coerce organisms into risky lotteries. Chance favors the prepared. The ‘Law of Requisite Variety’ holds that cybernetic systems must have internal variety that matches their external variety so that they can self-organize to fight variation with variation. Both conservative and diversifying bet-hedging are the risk-avoiding and -spreading insurance strategies in response to environmental uncertainty. The bet-hedging strategy tries to cover all bases in an often unpredictable environment where it does not make sense to “put all eggs into one basket”. In this sense, variation is the bad/worst-case insurance strategy of risk-aversive individuals. Variation is pervasive at every level of biological organization and is created by a multitude of processes: mutagenesis, epimutagenesis, recombination, transposon mobility, repeat instability, gene expression noise, cellular network dynamics, physiology, phenotypic plasticity, behavior, and life history strategy. Importantly, variation is created condition-dependently, when variation is most needed – in organisms under stress. The bet-hedging strategy also manifests in a multitude of life history patterns: turnover of generations, reproductive prudence, iteroparity, polyandry, and sexual reproduction.

Cybernetic systems are complex systems. Complexity is conceived as a system’s potential to assume a large number of states, i.e., variety. Complex systems have both stochastic and deterministic properties and, in fact, generate order from chaos. Non-linearity, criticality, self-organization, emergent properties, scaling, hierarchy and evolvability are features of complex systems. Emergent properties are features of a complex system that are not present at the lower level but arise unexpectedly from interactions among the system’s components. Only within an intermediate level of stochastic variation, somewhere between determined rigidity and literal chaos, local interactions can give rise to complexity. Stochastic environments change the rules of evolution. Lotteries cannot be played and insurance strategies not employed with single individuals. These are emergent population-level processes that exert population-level selection pressures generating variation and diversity at all levels of biological organization. Together with frequency and density-dependent selection, lottery- and insurance-dependent selection act on population-level traits.

The duality of stochasticity and selection is the organizing principle of evolution. Both are interdependent. The feedback between output and input signals inextricably intertwines both stochasticity and natural selection, and the individual- and population-levels of selection. Sexual reproduction with its generation of pre-selected variation is the paradigmatic bet-hedging enterprise and its evolutionary success is the selective signature of stochastic environments.Sexual reproduction is the proof of concept that (epi)genetic variation is no accidental occurrence but a highly regulated process and environmental stochasticity is its evolutionary “raison d’être”.Evolutionary biology is plaqued by a multitude of controversies (e.g. concerning the level of selection issue and sociobiology. Almost miraculously, these controversies can be resolved by the cybernetic model of evolution and its implications.

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