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The sexy son hypothesis in evolutionary biology and sexual selection — proposed by Ronald Fisher in 1930 — states that a female's ideal mate choice among potential mates is one whose genes will produce male offspring with the best chance of reproductive success and implies that a potential mate's capacity as a parental caregiver or any other direct benefits the father can offer the mother such as nuptial gifts, or good territory are irrelevant to his value as the potential father of the female's offspring. Fisher's principle means that the sex ratio (except in certain eusocial insects) is always 1:1 between males and females, yet what matters most are her "sexy sons"' future breeding successes, more likely if they have a promiscuous father, in creating large numbers of offspring carrying copies of her genes. This sexual selection hypothesis has been researched in species such as the European pied flycatcher. ==Context== Female mating preferences are widely recognized as being responsible for the rapid and divergent evolution of male secondary sex characteristics.〔Andersson M (1994). Sexual Selection. Princeton Univ Press, Princeton, NJ.〕 In 1976, prior to Weatherhead and Robertson's paper, Richard Dawkins had written in his book ''The Selfish Gene'': The sexy son hypothesis, published by Fisher in his book ''The Genetical Theory of Natural Selection'', is one of several possible explanations for the highly diverse and often astonishing ornaments of animals.〔Geoffrey Miller (2000). The Mating Mind. Anchor Books, a division of Random House, Inc. (First Anchor Books Edition, April 2001). New York, NY. Anchor ISBN 0-385-49517-X〕 If females choose physically attractive males, they will tend to get physically attractive sons, and, thus more grandchildren, because other choosy females will prefer their attractive, sexy sons. The theory will function regardless of the physical or behavioral trait a female chooses, as long as it is heritable (that is, the trait varies between individuals of the population), because it is possessing the trait that makes males attractive, and not the qualities of the trait in itself. Thus, traits culturally perceived as negative can still be seen as desirable; for example, females who stay with or are attracted to males they know to be disloyal in a monogamous relationship. If this trait is passed to any male children, they are more likely to themselves be non-monogamous, have several mates and spread the female's genes to multiple grandchildren. Once a preference becomes established, females choosing males with elaborate secondary sexual traits will produce sons that carry alleles for the trait and daughters that carry alleles for the preference, generating genetic coupling that will drive self-reinforcing coevolution of both trait and preference, due to the mating advantage of males with the trait, creating a Fisherian runaway sexy sons process.〔 Similar models have been proposed for postcopulatory female preferences, such as the time at which females removed the male's sperm ampulla after mating. Sexual selection by direct and/or indirect benefits as well as sexual conflict determine the evolution of animal mating systems. In its original context, the "narrow-sense sexy son hypothesis" of Weatherhead and Robertson refers to mating systems with care from both parents. In these mating systems, females that mate with a polygynous male normally receive less assistance than females mated with a monogamous male,〔Ligon JD. (1999). The evolution of avian breeding systems. New York: Oxford University Press.〕 and thus suffer from direct fitness consequences that have to be (at least) compensated for by the breeding successes of their sexy sons. On the other hand, a "broad-sense sexy son hypothesis" encompasses both polygyny and promiscuous mating systems, with and without care from both parents. Alatalo (1998)〔Alatalo R.V., (1998). Mate choice for offspring performance: major benefits or minor costs? Proc R Soc Lond B Biol Sci. vol 265, pp 2297-2297〕 argues that the costs of any additional choice may be so minor that female choice for honestly signaling males, that is good genes, may evolve even if the indirect benefits on offspring quality are small. A similar argument can be made for the sexy son hypothesis if mates of attractive males do not suffer any direct fitness consequences.〔Thomas Huk and Wolfgang Winkel, (2008). Testing the sexy son hypothesis—a research framework for empirical approaches. Behavioral Ecology (2008) vol 19, (2). pp 456-461. . First published online: January 18, 2008. Institute of Avian Research "Vogelwarte Helgoland," An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany. Address correspondence to T. Huk, who is now at Department of Business Administration, Economics, and Social Sciences, Technische Universität Braunschweig, Rebenring 58A, D-38106 Braunschweig, Germany.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sexy son hypothesis」の詳細全文を読む スポンサード リンク
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