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Fisherian runaway: Difference between revisions
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== Mechanism == | == Mechanism == | ||
[[File:Peacock courting peahen.jpg|alt=|thumb|"The females may be dull looking, but they're very picky." A peacock courting a peahen]] | [[File:Peacock courting peahen.jpg|alt=|thumb|"The females may be dull looking, but they're very picky." A peacock courting a peahen]] | ||
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 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 | 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 and rounder. | 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 rounder. | ||