Human Nature

, Volume 17, Issue 3, pp 253–264 | Cite as

Semen displacement as a sperm competition strategy

Multiple mating, self-semen displacement, and timing of in-pair copulations
  • Gordon G. GallupEmail author
  • Rebecca L. Burch
  • Tracy J. Berene Mitchell


Using a sample of 652 college students, we examined several implications of the hypothesis that the shape of the human penis evolved to enable males to substitute their semen for those of their rivals. The incidence of double mating by females appears sufficient to make semen displacement adaptive (e.g., one in four females acknowledge infidelity, one in eight admit having sex with two or more males in a 24-hour period, and one in 12 report involvement in one or more sexual threesomes with two males). We also document several changes in post-ejaculatory behavior (e.g., reduced thrusting, penis withdrawal, loss of an erection) which may have evolved to minimize displacement of the male’s own semen. Consistent with predictions derived from a theoretical model (Gallup and Burch 2006), we discovered that most females report waiting at least 48 hours following an instance of infidelity before resuming sex with their in-pair partners.

Key words

Cuckoldry Double mating Genital morphology Paternity Post-ejacu-latory changes Sperm competition 


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Copyright information

© Transaction Publishers 2006

Authors and Affiliations

  • Gordon G. Gallup
    • 1
    Email author
  • Rebecca L. Burch
    • 2
  • Tracy J. Berene Mitchell
    • 3
  1. 1.Department of PsychologyState University of New York at AlbanyAlbany
  2. 2.State University College at OswegoNew York
  3. 3.State University of New York at AlbanyUSA

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