Cavefish (without eyes) and surface dwelling brethren. (Image courtesy of New York University) (Credit: Image courtesy of New York University)

 Regressive evolution is a phenomenon by which a species loses features through evolution. It is especiall y evident in many cave-dwelling species, the majority of which actually descended from species that originally lived above ground. Some of these organisms happened to have traits that were beneficial in a cave environment, prompting part of the population to move underground. Over time some features, like eyes or skin pigmentation, for example, became unnecessary and eventually disappeared.


Astyanax cavefish have adapted to life in caves by loss of eyes and pigmentation. 


Retrieved from on November 28, 2013.

New York University (2007, February 16). 'Regressive Evolution' In Cavefish: Natural Selection Or Genetic Drift. ScienceDaily

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