Vestigiality
From The Art and Popular Culture Encyclopedia
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"Whereas useless in this circumstance, these rudiments... have not been eliminated, because Nature never works by rapid jumps, and She always leaves vestiges of an organ, even though it is completely superfluous, if that organ plays an important role in the other species of the same family."--Étienne Geoffroy Saint-Hilaire on vestigial structures, "Observations sur l'aile de l'Autruche, par le citoyen Geoffroy", La Decade Egyptienne, Journal Litteraire et D'Economie Politique 1 (pp. 46–51)., 1798 |
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Vestigiality is the retention during the process of evolution of genetically determined structures or attributes that have lost some or all of their ancestral function in a given species. Assessment of the vestigiality must generally rely on comparison with homologous features in related species. The emergence of vestigiality occurs by normal evolutionary processes, typically by loss of function of a feature that is no longer subject to positive selection pressures when it loses its value in a changing environment. The feature may be selected against more urgently when its function becomes definitively harmful, but if the lack of the feature provides no advantage, and its presence provides no disadvantage, the feature may not be phased out by natural selection and persist across species. Typical examples of both types occur in the loss of flying capability in island-dwelling species of birds.
See also
- Atavism
- Dewclaw
- Exaptation
- Human vestigiality
- Maladaptation
- Plantaris muscle
- Recessive refuge
- Spandrel (biology)
- Vestigial response
