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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, | 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 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, 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, 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. | ||
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Since females are [[Bateman's principle|more choosy]] in many species throughout the animal kingdom (including humans), the males tend to be more ornamented. | Since females are [[Bateman's principle|more choosy]] in many species throughout the animal kingdom (including humans), the males tend to be more ornamented. | ||
Another mechanism that could explain exaggerated ornament and the immense sexual attraction to it, could be [https://en.wikipedia.org/wiki/Handicap_principle Zahavi's handicap principle], also called ''good genes hypothesis'' which claims that exaggerated ornament is a costly and hence reliable signal of other desirable traits. For example, a peacock | Another mechanism that could explain exaggerated ornament and the immense sexual attraction to it, could be [https://en.wikipedia.org/wiki/Handicap_principle Zahavi's handicap principle], also called ''good genes hypothesis'' which claims that exaggerated ornament is a costly and hence reliable signal of other desirable traits. For example, a peacock with a very large tail would be easy prey (which is costly), hence must likely have other good traits that make up for it enabling his survival despite his handicap (good genes). There is, however, little supporting scientific evidence. In humans in particular, beauty is not strongly correlated with health at all, and even less with cognitive ability.<ref>https://incels.wiki/w/Scientific_Blackpill#Attractive_people_are_perceived_much_more_positively_than_they_really_are</ref> Neither does human ornament like seem to be particularly costly (except for tallness and large female breasts). | ||
== Peafowl == | == Peafowl == | ||