Baldwin effect
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The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is an early evolutionary theory proposed by American psychologist James Mark Baldwin which proposes a mechanism for specific selection for general learning ability. 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 behavior of a species or group can shape the evolution of that species.
In 1896, Baldwin proposed that individual learning can explain evolutionary phenomena that appear to support Lamarckian inheritance. He saw the Baldwin Effect, which he called organic selection, as a reconciliation between Lamarckian evolution and Darwinian evolution. It proposed that the ability of individuals to learn can guide the evolutionary process, facilitating evolution by smoothing the fitness landscape. Baldwin further proposed that abilities that initially require learning are eventually replaced by the evolution of genetically determined systems that do not require learning. Thus learned behaviors may become instinctive behaviours in subsequent generations, without invoking the discredited Lamarckian inheritance. Unlike Lamarckian evolution, it does not involve direct transfer of learned abilities from generation to generation.
As an example, suppose a species is threatened by a new predator and there is a behavior that makes it more difficult for the predator. Individuals who learn the behavior more quickly will obviously be at an advantage. As time goes on the ability to learn the behavior will improve (by genetic selection), and at some point it will seem to be an instinct.
The appearance of lactose tolerance in human populations with a long tradition of raising domesticated animals for milk production has been suggested as another example. This argument holds that a feedback loop operates whereby a dairy culture increases the selective advantage from this genetic trait, while the average population genotype increases the collective rewards of a dairy culture.
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- Baldwin, Mark J. A New Factor in Evolution. The American Naturalist, Vol. 30, No. 354 (Jun., 1896), 441-451.
- Osborn, Henry F. Ontogenic and Phylogenic Variation. Science, New Series, Vol. 4, No. 100 (Nov. 27, 1896), 786-789.
- Baldwin, Mark J. Organic Selection. Science, New Series, Vol. 5, No. 121 (Apr. 23, 1897), 634-636.
- Hall, Brian K. Organic Selection: Proximate Environmental Effects on the Evolution of Morphology and Behaviour. Biology and Philosophy 16: 215-237, 2001.
- Bateson, Patrick. The Active Role of Behaviour in Evolution. Biology and Philosophy 19: 283-298, 2004.
