, Volume 138, Issue 1, pp 5–18 | Cite as

Evolution of genitalia: theories, evidence, and new directions

  • William G. EberhardEmail author


Many hypotheses have been proposed to explain why male intromittent genitalia consistently tend to diverge more rapidly than other body traits of the same individuals in a wide range of animal taxa. Currently the two most popular involve sexual selection: sexually antagonistic coevolution (SAC) and cryptic female choice (CFC). A review of the most extensive attempts to discriminate between these two hypotheses indicates that SAC is not likely to have played a major role in explaining this pattern of genital evolution. Promising lines for future, more direct tests of CFC include experimental modification of male genital form and female sensory abilities, analysis of possible male–female dialogues during copulation, and direct observations of genital behavior.


Sexual conflict Sexual selection Sexually antagonistic coevolution Cryptic female choice 



I am extremely grateful to Michael Schmitt and Dominique Joly for honoring me by organizing a symposium on genital evolution. I also thank Daniel Briceño, Marie Djernaes, Rudolf Meier, Alfredo Peretti, Hojun Song, and Nick Tatarnic for access to unpublished work, Y. Kamimura and P. Schmid-Hempel for permission to quote personal communications, David Hosken, Santosh Jagadeeshan, Dominique Joly, Rafael Lucas Rodriguez, and two referees for useful comments. My research was supported financially by the Smithsonian Tropical Research Institute and the Universidad de Costa Rica.


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Authors and Affiliations

  1. 1.Smithsonian Tropical Research Institute, and Escuela de BiologíaUniversidad de Costa Rica, Ciudad UniversitariaSan PedroCosta Rica

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