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Fisherian runaway: Difference between revisions
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Fisherian runaway is a feedback loop occurring over many generations, in which the one sex becomes more choosy about a heritable trait for the simple reason that others find the trait attractive. As the the choosiness for the trait increases, the selective pressure to prefer the trait increases too, forming a [https://en.wikipedia.org/wiki/Positive_feedback_loop positive feedback loop]. In response to the increased choosiness, the other sex evolves to enlarge, overcomplicate or beautify that trait in efforts of becoming more attractive. The exponential nature of positive feedback loops exerts a strong selection pressure that can even overcome the selective pressure for survival itself and hence lead to extinction. | Fisherian runaway is a feedback loop occurring over many generations, in which the one sex becomes more choosy about a heritable trait for the simple reason that others find the trait attractive. As the the choosiness for the trait increases, the selective pressure to prefer the trait increases too, forming a [https://en.wikipedia.org/wiki/Positive_feedback_loop positive feedback loop]. In response to the increased choosiness, the other sex evolves to enlarge, overcomplicate or beautify that trait in efforts of becoming more attractive. The exponential nature of positive feedback loops exerts a strong selection pressure that can even overcome the selective pressure for survival itself and hence lead to extinction. | ||
Such feedback loops can be initiated by arbitrary aesthetic selection, but also when a trait is slightly correlated with fitness (e.g. health), or when a trait is similar in appearance to attractive or otherwise valuable objects or body parts.<ref>Fuller, R. C., Houle, D., & Travis, J. 2005. ''Sensory Bias as an Explanation for the Evolution of Mate Preferences.'' [[https://www.jstor.org/stable/10.1086/444443 Abstract]], p. 444</ref> For example, women's breasts may have evolved to mimic their buttocks because the latter was already a sexually attractive body part before humans developed upright posture, and then Fisherian runaway may have lead to breasts becoming increasingly larger. | Such feedback loops can be initiated by arbitrary aesthetic selection, but also when a trait is slightly correlated with fitness (e.g. health), or when a trait is similar in appearance to attractive or otherwise valuable objects or body parts.<ref>Fuller, R. C., Houle, D., & Travis, J. 2005. ''Sensory Bias as an Explanation for the Evolution of Mate Preferences.'' [[https://www.jstor.org/stable/10.1086/444443 Abstract]], p. 444</ref> For example, women's breasts may have evolved to mimic their buttocks because the latter was already a sexually attractive body part before humans developed upright posture, and then Fisherian runaway may have lead to breasts becoming increasingly larger and increasingly attractive to men. | ||
In summary, beauty could have evolved simply by sexual selection, i.e. mate selection favoring objectively good looks (simplicity). But feedback loops as mentioned above may have exaggerated aspects of it, leading to increased sexual dimorphism and amplified and narrowed the attraction to specific kinds of beautiful phenotypes. This also leads to a stabilization of the phenotype. | In summary, beauty could have evolved simply by sexual selection, i.e. mate selection favoring objectively good looks (simplicity). But feedback loops as mentioned above may have exaggerated aspects of it, leading to increased sexual dimorphism and amplified and narrowed the attraction to specific kinds of beautiful phenotypes. This also leads to a stabilization of the phenotype. | ||