Baldwin effect

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File:Lamarck Compared to Darwin, Baldwin, Waddington.svg

The Baldwin effect compared to Lamarck's theory of evolution, Darwinian evolution, and Waddington's genetic assimilation. All the theories offer explanations of how organisms respond to a changed environment with adaptive inherited change.

In evolutionary biology, the Baldwin effect describes an effect of learned behaviour on evolution. James Mark Baldwin and others suggested that an organism's ability to learn new behaviours (e.g. to acclimatise to a new stressor) will affect its reproductive success and will therefore have an effect on the genetic makeup of its species through natural selection. It posits that subsequent selection might reinforce the originally learned behaviors, if adaptive, into more in-born, instinctive ones. Though this process appears similar to Lamarckism, that view proposes that living things inherited their parents' acquired characteristics. The Baldwin effect only posits that learning ability, which is genetically based, is another variable in / contributor to environmental adaptation. First proposed during the Eclipse of Darwinism in the late 19th century, this effect has been independently proposed several times, and today it is generally recognized as part of the modern synthesis.

"A New Factor in Evolution"Edit

The effect, then unnamed, was put forward in 1896 in a paper "A New Factor in Evolution" by the American psychologist James Mark Baldwin, with a second paper in 1897.Template:Sfn Template:Sfn The paper proposed a mechanism for specific selection for general learning ability. As the historian of science Robert Richards explains:<ref name=Richards1987>Template:Cite book</ref>

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Selected offspring would tend to have an increased capacity for learning new skills rather than being confined to genetically coded, relatively fixed abilities. In effect, it places emphasis on the fact that the sustained behaviour of a species or group can shape the evolution of that species. The "Baldwin effect" is better understood in evolutionary developmental biology literature as a scenario in which a character or trait change occurring in an organism as a result of its interaction with its environment becomes gradually assimilated into its developmental genetic or epigenetic repertoire.Template:Sfn Template:Sfn In the words of the philosopher of science Daniel Dennett:<ref name=dennett03/>

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An update to the Baldwin effect was developed by Jean Piaget, Paul Weiss, and Conrad Waddington in the 1960s–1970s. This new version included an explicit role for the social in shaping subsequent natural change in humans (both evolutionary and developmental), with reference to alterations of selection pressures.<ref>Template:Cite journal</ref>

Subsequent research shows that Baldwin was not the first to identify the process; Douglas Spalding mentioned it in 1873.<ref>Noble, R.; Noble, D. (2017) Was the Watchmaker Blind? Or Was She One-Eyed? Biology 2017, 6(4), 47; doi:10.3390/biology6040047, quoting Bateson, P. The adaptability driver: Links between behaviour and evolution. Biol. Theory 2006, 1, 342–345. See also Stigler's law.</ref>

Controversy and acceptanceEdit

Initially Baldwin's ideas were not incompatible with the prevailing, but uncertain, ideas about the mechanism of transmission of hereditary information and at least two other biologists put forward very similar ideas in 1896.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> In 1901, Maurice Maeterlinck referred to behavioural adaptations to prevailing climates in different species of bees as "what had merely been an idea, therefore, and opposed to instinct, has thus by slow degrees become an instinctive habit".<ref>Template:Cite book</ref> The Baldwin effect theory subsequently became more controversial, with scholars divided between "Baldwin boosters" and "Baldwin skeptics".<ref name="depew03">Depew, David J. (2003), "Baldwin Boosters, Baldwin Skeptics" in: Template:Cite book</ref> The theory was first called the "Baldwin effect" by George Gaylord Simpson in 1953.<ref name="depew03"/> Simpson "admitted that the idea was theoretically consistent, that is, not inconsistent with the modern synthesis",<ref name="depew03"/> but he doubted that the phenomenon occurred very often, or if so, could be proven to occur. In his discussion of the reception of the Baldwin-effect theory Simpson points out that the theory appears to provide a reconciliation between a neo-Darwinian and a neo-Lamarckian approach and that "Mendelism and later genetic theory so conclusively ruled out the extreme neo-Lamarckian position that reconciliation came to seem unnecessary".Template:Sfn In 1942, the evolutionary biologist Julian Huxley promoted the Baldwin effect as part of the modern synthesis, saying the concept had been unduly neglected by evolutionists.Template:Sfn<ref name="Scheiner 2014">Template:Cite journal</ref><ref name="Belew 2018">Template:Cite book</ref>

In the 1960s, the evolutionary biologist Ernst Mayr contended that the Baldwin effect theory was untenable because

the argument is stated in terms of the individual genotype, whereas what is really exposed to the selection pressure is a phenotypically and genetically variable population;
it is not sufficiently emphasized that the degree of modification of the phenotype is in itself genetically controlled;
it is assumed that phenotypic rigidity is selectively superior to phenotypic flexibility.<ref name="Mayr1963">Template:Cite book</ref>

In 1987 Geoffrey Hinton and Steven Nowlan demonstrated by computer simulation that learning can accelerate evolution, and they associated this with the Baldwin effect.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name=Puentedura2003>Template:Cite book</ref>

Paul Griffiths<ref name="Griffiths2003">Template:Cite book</ref> suggests two reasons for the continuing interest in the Baldwin effect. The first is the role mind is understood to play in the effect. The second is the connection between development and evolution in the effect. Baldwin's account of how neurophysiological and conscious mental factors may contribute to the effect<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>Template:Sfn brings into focus the question of the possible survival value of consciousness.<ref name=Lindahl2001>Template:Cite book</ref>

File:Carpodacus mexicanus -Madison, Wisconsin, USA-8.jpg

The house finch's colonisation of North America has provided empirical evidence of the Baldwin effect.<ref name=Badyaev/>

Still, David Depew observed in 2003, "it is striking that a rather diverse lot of contemporary evolutionary theorists, most of whom regard themselves as supporters of the Modern Synthesis, have of late become 'Baldwin boosters'".<ref name="depew03" /> These

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According to Dennett, also in 2003, recent work has rendered the Baldwin effect "no longer a controversial wrinkle in orthodox Darwinism".<ref name="dennett03">Dennett, Daniel (2003), "The Baldwin Effect: a Crane, not a Skyhook" in: Template:Cite book</ref> Potential genetic mechanisms underlying the Baldwin effect have been proposed for the evolution of natural (genetically determinant) antibodies.<ref>Template:Cite journal</ref> In 2009, empirical evidence for the Baldwin effect was provided from the colonisation of North America by the house finch.<ref name=Badyaev>Template:Cite journal</ref>

The Baldwin effect has been incorporated into the extended evolutionary synthesis.<ref>Pigliucci, Massimo. Phenotypic Plasticity. In Massimo Pigliucci, and Gerd B. Müller (eds), Evolution: The Extended Synthesis (Cambridge, MA, 2010; online edn, MIT Press Scholarship Online, 22 Aug. 2013).</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Comparison with genetic assimilationEdit

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The Baldwin effect has been confused with, and sometimes conflated with, a different evolutionary theory also based on phenotypic plasticity, C. H. Waddington's genetic assimilation. The Baldwin effect includes genetic accommodation, of which one type is genetic assimilation.<ref>Template:Cite journal</ref> Science historian Laurent Loison has written that "the Baldwin effect and genetic assimilation, even if they are quite close, should not be conflated".<ref>Template:Cite journal</ref>

Baldwin effect

Contents

"A New Factor in Evolution"Edit

Controversy and acceptanceEdit

Comparison with genetic assimilationEdit

See alsoEdit

NotesEdit

ReferencesEdit

External linksEdit