Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
Hostname: page-component-7479d7b7d-68ccn Total loading time: 0 Render date: 2024-07-12T18:09:21.290Z Has data issue: false hasContentIssue false

11 - Sperm Competition Theory

from Part II - Middle-Level Theories

Published online by Cambridge University Press:  30 June 2022

By
Tara DeLecce
Edited by
Todd K. Shackelford
Todd K. Shackelford
Affiliation:
Oakland University, Michigan
Get access

Summary

Sperm competition occurs when a female copulates with two or more males within a sufficiently brief period, resulting in sperm of the different males competing to fertilize ova. Sperm competition has been documented or inferred to occur across many species, ranging from insects to primates, including humans. To open the chapter, the theory of sperm competition is introduced and the role of sperm competition as a recurrent adaptive problem for humans is highlighted. Because sperm competition could be detrimental to male reproductive success through cuckoldry, males have likely evolved anti-cuckoldry adaptations. Therefore, convergent evidence of anatomical, genetic, and physiological adaptations to sperm competition in human males is presented. This is followed by a discussion of behavioral and psychological evidence that is unique to humans and that differentiates them from nonhuman species, such as negative affect in response to sexual rejection by a man’s female partner. The remainder of the chapter is devoted to issues still debated within sperm competition theory, such as male precedence, intensity of sperm competition, the role of sperm heteromorphism, and the relationship between male phenotypic quality and ejaculate quality. The chapter concludes with the message that the evidence for anatomical, biological, physiological, genetic, and behavioral adaptations to human sperm competition provides compelling evidence that sperm competition has been a recurrent feature of human evolutionary history.

Keywords

sperm competitionanti-cuckoldry tacticsejaculate adjustmentsemen displacementsperm heteromorphism
Type
Chapter
Information
The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology , pp. 242 - 263
Publisher: Cambridge University Press
Print publication year: 2022

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Anderson, K. (2006). How well does paternity confidence match actual paternity? Evidence from worldwide nonpaternity rates. Current Anthropology, 47, 513–520.Google Scholar
Angulo, J., & García, M. (2005). Sex in stone: Sexuality, reproduction, and eroticism in the Paleolithic epoch. Madrid: Luzán.Google Scholar
Arden, R., Gottfredson, L. S., Miller, G. F., & Pierce, A. (2009). Intelligence and semen quality are positively correlated. Intelligence, 37, 277–282.CrossRefGoogle Scholar
Ariely, D., & Loewenstein, G. (2006). The heat of the moment: The effect of sexual arousal on sexual decision making. Journal of Behavioral Decision Making, 19, 87–98.Google Scholar
Arnocky, S., Sunderani, S., Gomes, W., & Vaillancourt, T. (2015). Anticipated partner infidelity and men’s intimate partner violence: The mediating role of anxiety. Evolutionary Behavioral Sciences, 9, 186.Google Scholar
Auger, J., Kunstmann, J. M., Czyglik, F., & Jouannet, P. (1995). Decline in semen quality among fertile men in Paris during the past 20 years. New England Journal of Medicine, 332, 281–285.Google Scholar
Baker, R. R., & Bellis, M. A. (1988). “Kamikaze” sperm in mammals? Animal Behaviour, 36, 936–939.Google Scholar
Baker, R. R., & Bellis, M. A. (1993a). Human sperm competition: Ejaculate adjustment by males and the function of masturbation. Animal Behaviour, 46, 861–885.Google Scholar
Baker, R. R., & Bellis, M. A. (1993b). Human sperm competition: Ejaculate manipulation by females and a function for the female orgasm. Animal Behaviour, 46, 887–909.Google Scholar
Baker, R. R., & Bellis, M. A. (1995). Human sperm competition: Copulation, masturbation and infidelity. London: Chapman & Hall.Google Scholar
Baker, R. R., & Shackelford, T. K. (2018). A comparison of paternity data and relative testes size as measures of level of sperm competition in the Hominoidea. American Journal of Physical Anthropology, 165, 421–443.Google Scholar
Barash, D. P. (1977). Sociobiology of rape in mallards (Anas platyrhynchos): Responses of the mated male. Science, 197, 788–789.Google Scholar
Bellis, M. A., Hughes, K., Hughes, S., & Ashton, J. R. (2005). Measuring paternal discrepancy and its public health consequences. Journal of Epidemiology & Community Health, 59, 749–754.Google Scholar
Bostofte, E., Serup, J., & Rebbe, H. (1983). Has the fertility of Danish men declined through the years in terms of semen quality? A comparison of semen qualities between 1952 and 1972. International Journal of Fertility, 28, 91–95.Google Scholar
Brewis, A., & Meyer, M. (2005). Demographic evidence that human ovulation is undetectable (at least in pair bonds). Current Anthropology, 46, 465–471.Google Scholar
Camilleri, J. A., & Quinsey, V. L. (2009). Testing the cuckoldry risk hypothesis of partner sexual coercion in community and forensic samples. Evolutionary Psychology, 7, 164–178.CrossRefGoogle Scholar
Candolin, U., & Reynolds, J. D. (2002). Adjustments of ejaculation rates in response to risk of sperm competition in a fish, the bitterling (Rhodeus sericeus). Proceedings of the Royal Society of London. Series B: Biological Sciences, 269, 1549–1553.Google Scholar
Chavanne, T. J., & Gallup, G. G. Jr. (1998). Variation in risk taking behavior among female college students as a function of the menstrual cycle. Evolution and Human Behavior, 19, 27–32.Google Scholar
Cheng, K. M., Burns, J. T., & McKinney, F. (1983). Forced copulation in captive mallards III: Sperm competition. The Auk, 100, 302–310.Google Scholar
Clark, N. L., & Swanson, W. J. (2005). Pervasive adaptive evolution in primate seminal proteins. PLoS Genetics, 1, e35.Google Scholar
Cohen, J. (1973). Crossovers, sperm redundancy, and their close association. Heredity, 31, 408–413.Google Scholar
Cornwallis, C. K., & O’Connor, E. A. (2009). Sperm: Seminal fluid interactions and the adjustment of sperm quality in relation to female attractiveness. Proceedings of the Royal Society of London. Series B: Biological Sciences, 276, 3467–3475.Google Scholar
DeLecce, T., Barbaro, N., Mohamedally, D., & Shackelford, T. K. (2017). Husband’s reaction to his wife’s sexual rejection is predicted by the time she spends with her male friends, but not her male coworkers. Evolutionary Psychology, 15, 1–5.Google Scholar
DeLecce, T., Fink, B., Shackelford, T., & Abed, M. G. (2020). No evidence for a relationship between intelligence and ejaculate quality. Evolutionary Psychology, 18(3), 1474704920960450.Google Scholar
DeLecce, T., Shackelford, T. K., Fink, B., & Abed, M. G. (2020). No evidence for a trade-off between competitive traits and ejaculate quality in humans. Evolutionary Psychology, 18, 1474704920942557.Google Scholar
DeLecce, T., Shackelford, T. K., Zeigler-Hill, , Fink, B., & Abed, M. G. (in press). Mate retention behaviors and ejaculate quality in humans. Archives of Sexual Behavior.Google Scholar
Dorus, S., Evans, P. D., Wyckoff, G. J., Choi, S. S., & Lahn, B. T. (2004). Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity. Nature Genetics, 36, 1326–1329.Google Scholar
Finkelhor, D., & Yllo, K. (1985). License to rape: Sexual abuse of wives. New York, NY: Holt, Rinehart, & Winston.Google Scholar
Foo, Y. Z., Simmons, L. W., Peters, M., & Rhodes, G. (2018). Perceived physical strength in men is attractive to women but may come at a cost to ejaculate quality. Animal Behavior, 142, 191–197.Google Scholar
Frieze, I. H. (1983). Investigating the causes and consequences of marital rape. Signs: Journal of Women in Culture and Society, 8, 532–553.Google Scholar
Gage, A. J., & Hutchinson, P. L. (2006). Power, control, and intimate partner sexual violence in Haiti. Archives of Sexual Behavior, 35, 11–24.Google Scholar
Gage, A. R., & Barnard, C. J. (1996). Male crickets increase sperm number in relation to competition and female size. Behavioral Ecology and Sociobiology, 38, 349–353.Google Scholar
Gallup, G. G. Jr., & Burch, R. L. (2004). Semen displacement as a sperm competition strategy in humans. Evolutionary Psychology, 2, 12–23.Google Scholar
Gallup, G. G., Burch, R. L., & Mitchell, T. J. B. (2006). Semen displacement as a sperm competition strategy: Multiple mating, self-semen displacement, and timing of in-pair copulations. Human Nature, 17, 253–264.Google Scholar
Gallup, G. G. Jr., Burch, R. L., & Petricone, L. R. (2012). Sexual conflict, infidelity, and vaginal/semen chemistry. In Shackelford, T. K. & Goetz, A. T. (Eds.), The Oxford handbook of sexual conflict in humans (pp. 217–231). New York, NY: Oxford University Press.Google Scholar
Gallup, G. G. Jr., Burch, R. L., Zappieri, M. L., Parvez, R. A., Stockwell, M. L., & Davis, J. A. (2003). The human penis as a semen displacement device. Evolution and Human Behavior, 24, 277–289.Google Scholar
Gangestad, S. W., Thornhill, R., & Garver-Apgar, C. E. (2005). Women’s sexual interests across the ovulatory cycle depend on primary partner developmental instability. Proceedings of the Royal Society of London. Series B: Biological Sciences, 272, 2023–2027.Google Scholar
Goetz, A. T., & Shackelford, T. K. (2006). Sexual coercion and forced in-pair copulation as sperm competition tactics in humans. Human Nature, 17, 265–282.Google Scholar
Goetz, A. T., & Shackelford, T. K. (2009). Sexual coercion in intimate relationships: A comparative analysis of the effects of women’s infidelity and men’s dominance and control. Archives of Sexual Behavior, 38, 226–234.Google Scholar
Goetz, A. T., Shackelford, T. K., & Camilleri, J. A. (2008). Proximate and ultimate explanations are required for a comprehensive understanding of partner rape. Aggression and Violent Behavior, 13, 119–123.Google Scholar
Goetz, A. T., Shackelford, T. K., Platek, S. M., Starratt, V. G., & McKibbin, W. F. (2007). Sperm competition in humans: Implications for male sexual psychology, physiology, anatomy, and behavior. Annual Review of Sex Research, 18, 1–22.Google Scholar
Goetz, A. T., Shackelford, T. K., Weekes-Shackelford, V. A., Euler, H. A., Hoier, S., Schmitt, D. P., & LaMunyon, C. W. (2005). Mate retention, semen displacement, and human sperm competition: A preliminary investigation of tactics to prevent and correct female infidelity. Personality and Individual Differences, 38, 749–763.Google Scholar
Gottschall, J. (2004). Explaining wartime rape. Journal of Sex Research, 41, 129–136.Google Scholar
Gottschall, J. A., & Gottschall, T. A. (2003). Are per-incident rape-pregnancy rates higher than per-incident consensual pregnancy rates? Human Nature, 14, 1–20.Google Scholar
Guadamuz, T. E., Kunawararak, P., Beyrer, C., Pumpaisanchai, J., Wei, C., & Celentano, D. D. (2010). HIV prevalence, sexual and behavioral correlates among Shan, Hill tribe, and Thai male sex workers in Northern Thailand. AIDS Care, 22, 597–605.Google Scholar
Guéguen, N. (2012). Gait and menstrual cycle: Ovulating women use sexier gaits and walk slowly ahead of men. Gait & Posture, 35, 621–624.Google Scholar
Gunns, R. E., Johnston, L., & Hudson, S. M. (2002). Victim selection and kinematics: A point-light investigation of vulnerability to attack. Journal of Nonverbal Behavior, 26, 129–158.Google Scholar
Hald, G. M. (2006). Gender differences in pornography consumption among young heterosexual Danish adults. Archives of Sexual Behavior, 35, 577–585.Google Scholar
Halpern, J., & Sherman, M. A. (1979). Afterplay: A key to intimacy. New York, NY: Pocket Books.Google Scholar
Harcourt, A. H. (1989). Deformed sperm are probably not adaptive. Animal Behaviour, 37, 863–865.Google Scholar
Haselton, M. G., & Gildersleeve, K. (2011). Can men detect ovulation? Current Directions in Psychological Science, 20, 87–92.Google Scholar
Haselton, M. G., Mortezaie, M., Pillsworth, E. G., Bleske-Rechek, A., & Frederick, D. A. (2007). Ovulatory shifts in human female ornamentation: Near ovulation, women dress to impress. Hormones and Behavior, 51, 40–45.Google Scholar
Hewlett, B. S., & Hewlett, B. L. (2010). Sex and searching for children among Aka foragers and Ngandu farmers of Central Africa. African Study Monographs, 31, 107–125.Google Scholar
Holman, L., & Snook, R. R. (2006). Spermicide, cryptic female choice and the evolution of sperm form and function. Journal of Evolutionary Biology, 19, 1660–1670.Google Scholar
Hosken, D. J., & Ward, P. I. (2001). Experimental evidence for testis size evolution via sperm competition. Ecology Letters, 4, 10–13.Google Scholar
Iwawaki, S., & Wilson, G. D. (1983). Sex fantasies in Japan. Personality and Individual Differences, 4, 543–545.CrossRefGoogle Scholar
Jeffery, A. J., Pham, M. N., Shackelford, T. K., & Fink, B. (2016). Does human ejaculate quality relate to phenotypic traits? American Journal of Human Biology, 38, 318–329.Google Scholar
Kaighobadi, F., & Shackelford, T. K. (2008). Female attractiveness mediates the relationship between in-pair copulation frequency and men’s mate retention behaviors. Personality and Individual Differences, 45, 293–295.Google Scholar
Kilgallon, S. J., & Simmons, L. W. (2005). Image content influences men’s semen quality. Biology Letters, 1, 253–255.Google Scholar
Klusmann, D. (2002). Sexual motivation and the duration of partnership. Archives of Sexual Behavior, 31, 275–287.Google Scholar
Klusmann, D. (2006). Sperm competition and female procurement of male resources. Human Nature, 17, 283–300.Google Scholar
Krejčová, L., Kuba, R., Flegr, J., & Klapilová, K. (2020). Kamasutra in practice: The use of sexual positions in the Czech population and their association with female coital orgasm potential. Sexual Medicine, 8, 767–776.Google Scholar
Kura, T., & Nakashima, Y. (2000). Conditions for the evolution of soldier sperm classes. Evolution, 54, 72–80.Google Scholar
Larmuseau, M. H., Matthijs, K., & Wenseleers, T. (2016). Cuckolded fathers rare in human populations. Trends in Ecology & Evolution, 31, 327–329.Google Scholar
Lee, S. (1988). Sperm preparation for assisted conception. Conceive, 12, 4–5.Google Scholar
Leivers, S., Rhodes, G., & Simmons, L. W. (2014). Sperm competition in humans: Mate guarding behavior negatively correlates with ejaculate quality. PLoS One, 9, e108099.Google Scholar
Leivers, S., & Simmons, L. W. (2014). Human sperm competition: Playing a defensive strategy. Advances in the Study of Behavior, 46, 1–44.Google Scholar
Locatello, L., Rasotto, M. B., Evans, J. P., & Pilastro, A. (2006). Colourful male guppies produce faster and more viable sperm. Journal of Evolutionary Biology, 19, 1595–1602.CrossRefGoogle ScholarPubMed
Lorch, P. D., Wilkinson, G. S., & Reillo, P. R. (1993). Copulation duration and sperm precedence in the stalk-eyed fly Cyrtodiopsis whitei (Diptera: Diopsidae). Behavioral Ecology and Sociobiology, 32, 303–311.Google Scholar
Lurie, P., Fernandes, M. E. L., Hughes, V., Arevalo, E. I., Hudes, E. S., Reingold, A., & Hearst, N. (1995). Socioeconomic status and risk of HIV-1, syphilis and hepatitis B infection among sex workers in São Paulo State, Brazil. AIDS, 9, 31–37.Google ScholarPubMed
Malamuth, N. M. (1996). Sexually explicit media, gender differences and evolutionary theory. Journal of Communication, 46, 8–31.Google Scholar
Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and concentration of testosterone luteinizing hormone and oestrogen. Human Reproduction, 13, 3000–3004.Google Scholar
Maruthupandian, J., & Marimuthu, G. (2013). Cunnilingus apparently increases duration of copulation in the Indian flying fox, Pteropus giganteus. PLoS One, 8, e59743.Google Scholar
Mauras, N., Bell, J., Snow, B. G., & Winslow, K. L. (2005). Sperm analysis in growth hormone-deficient adolescents previously treated with an aromatase inhibitor: Comparison with normal controls. Fertility and Sterility, 84, 239–242.Google Scholar
McCallum, C. (1994). Ritual and the origin of sexuality in the Alto Xingu. In Harvey, P. & Gow, P. (Eds.), Sex and violence: Issues in representation and experience (pp. 90–114). New York, NY: Routledge.Google Scholar
McKibbin, W. F., Pham, M. N., & Shackelford, T. K. (2013). Human sperm competition in postindustrial ecologies: Sperm competition cues predict adult DVD sales. Behavioral Ecology, 24, 819–823.CrossRefGoogle Scholar
McKibbin, W. F., Starratt, V. G., Shackelford, T. K., & Goetz, A. T. (2011). Perceived risk of female infidelity moderates the relationship between objective risk of female infidelity and sexual coercion in humans (Homo sapiens). Journal of Comparative Psychology, 125, 370–373.Google Scholar
Mineau, P., & Cooke, F. (1979). Rape in the lesser snow goose. Behaviour, 70, 280–291.Google Scholar
Moore, H. D. M., Martin, M., & Birkhead, T. R. (1999). No evidence for killer sperm or other selective interactions between human spermatozoa in ejaculates of different males in vitro. Proceedings of the Royal Society of London. Series B: Biological Sciences, 266, 2343–2350.Google Scholar
Mosher, D. L. (1988). Pornography defined: Sexual involvement theory, narrative context, and goodness-of-fit. Journal of Psychology & Human Sexuality, 1, 67–85.Google Scholar
Mougeot, F., Arroyo, B. E., & Bretagnolle, V. (2001). Decoy presentations as a means to manipulate the risk of extrapair copulation: An experimental test of paternity assurance strategies in a semi-colonial raptor, the Montagu’s Harrier Circus pygargus. Behavioural Ecology, 12, 1–7.Google Scholar
Nicholls, E. H., Burke, T., & Birkhead, T. R. (2001). Ejaculate allocation by male sand martins, Riparia riparia. Proceedings of the Royal Society of London. Series B: Biological Sciences, 268, 1265–1270.Google Scholar
Nishimura, K., Utsumi, K., Okano, T., & Iritani, A. (1991). Separation of mounting-inducing pheromones of vaginal mucus from estrual heifers. Journal of Animal Science, 69, 3343–3347.Google Scholar
O’Donohue, W., & Plaud, J. J. (1991). The long-term habituation of sexual arousal in the human male. Journal of Behavior Therapy and Experimental Psychiatry, 22, 87–96.Google Scholar
Ono, T., Siva‐Jothy, M. T., & Kato, A. K. I. (1989). Removal and subsequent ingestion of rivals’ semen during copulation in a tree cricket. Physiological Entomology, 14, 195–202.Google Scholar
Palagi, E., Telara, S., & Tarli, S. B. (2003). Sniffing behavior in Lemur catta: Seasonality, sex, and rank. International Journal of Primatology, 24, 335–350.CrossRefGoogle Scholar
Parker, G. A. (1970). Sperm competition and its evolutionary consequences in the insects. Biological Reviews, 45, 525–567.Google Scholar
Parker, G. A. (1990). Sperm competition games: Raffles and roles. Proceedings of the Royal Society of London. Series B: Biological Sciences, 242, 120–126.Google Scholar
Pham, M. N., Barbaro, N., Holub, A., Holden, C. J., Mogilski, J. K., Lopes, G. S., … Welling, L. L. M. (2018). Do men produce higher-quality ejaculates when primed with thoughts of partner infidelity? Evolutionary Psychology, 16, 1–7.Google Scholar
Pham, M. N., DeLecce, T., & Shackelford, T. K. (2017). Sperm competition in marriage: Semen displacement, male rivals, and spousal discrepancy in sexual interest. Personality and Individual Differences, 105, 229–232.Google Scholar
Pham, M. N., & Shackelford, T. K. (2013a). The relationship between objective sperm competition risk and men’s copulatory interest is moderated by partner’s time spent with other men. Human Nature, 24, 476–485.Google Scholar
Pham, M. N., & Shackelford, T. K. (2013b). Oral sex as infidelity-detection. Personality and Individual Differences, 54, 792–795.Google Scholar
Pham, M. N., Shackelford, T. K., Holden, C. J., Zeigler-Hill, V., Hummel, A., & Memering, S. L. (2014). Partner attractiveness moderates the relationship between number of sexual rivals and in-pair copulation frequency in humans (Homo sapiens). Journal of Comparative Psychology, 128, 328–331.Google Scholar
Pizzari, T., Cornwallis, C. K., Løvlie, H., Jakobsson, S., & Birkhead, T. R. (2003). Sophisticated sperm allocation in male fowl. Nature, 426, 70–74.Google Scholar
Pound, N. (2002). Male interest in visual cues of sperm competition risk. Evolution and Human Behavior, 23, 443–466.Google Scholar
Price, J. H., & Miller, P. A. (1984). Sexual fantasies of Black and of White college students. Psychological Reports, 54, 1007–1014.Google Scholar
Ramm, S. A., Parker, G. A., & Stockley, P. (2005). Sperm competition and the evolution of male reproductive anatomy in rodents. Proceedings of the Royal Society of London. Series B: Biological Sciences, 272, 949–955.Google Scholar
Russell, D. E. H. (1982). Rape in marriage. New York, NY: Macmillan.Google Scholar
Sadler, A. G., Booth, B. M., & Doebbeling, B. N. (2005). Gang and multiple rapes during military service: Health consequences and health care. Journal of the American Medical Women’s Association, 60, 33–41.Google Scholar
Sanday, P. R. (1981). The socio‐cultural context of rape: A cross‐cultural study. Journal of Social Issues, 37, 5–27.Google Scholar
Sanday, P. (2007). Fraternity gang rape: Sex, brotherhood, and privilege on campus. New York, NY: NYU Press.Google Scholar
Scelza, B. A., Prall, S. P., Swinford, N., Gopalan, S., Atkinson, E. G., McElreath, R., … Henn, B. M. (2020). High rate of extrapair paternity in a human population demonstrates diversity in human reproductive strategies. Science Advances, 6, eaay6195.Google Scholar
Shackelford, T. K., & Goetz, A. T. (Eds.). (2012). The Oxford handbook of sexual conflict in humans. New York, NY: Oxford University Press.Google Scholar
Shackelford, T. K., Goetz, A. T., Guta, F. E., & Schmitt, D. P. (2006). Mate guarding and frequent in-pair copulation in humans. Human Nature, 17, 239–252.Google Scholar
Shackelford, T. K., Goetz, A. T., LaMunyon, C. W., Quintus, B. J., & Weekes-Shackelford, V. A. (2004). Sex differences in sexual psychology produce sex-similar preferences for a short-term mate. Archives of Sexual Behavior, 33, 405–412.Google Scholar
Shackelford, T. K., Goetz, A. T., McKibbin, W. F., & Starratt, V. G. (2007). Absence makes the adaptations grow fonder: Proportion of time apart from partner, male sexual psychology, and sperm competition in humans (Homo sapiens). Journal of Comparative Psychology, 121, 214–220.CrossRefGoogle ScholarPubMed
Shackelford, T. K., LeBlanc, G. J., Weekes-Shackelford, V. A., Bleske-Rechek, A. L., Euler, H. A., & Hoier, S. (2002). Psychological adaptation to human sperm competition. Evolution and Human Behavior, 23, 123–138.Google Scholar
Sheldon, B. C. (1994). Male phenotype fertility and the pursuit of extra-pair copulations by female birds. Proceedings of the Royal Society of London, Series B: Biological Sciences, 257, 25–30.Google Scholar
Short, R. V. (1981). Sexual selection in man and the apes. In Graham, C. E. (Ed.), Reproductive biology of the great apes (pp. 319–341). New York, NY: Academic Press.Google Scholar
Simmons, L. W., & Emlen, D. J. (2006). Evolutionary trade-off between weapons and testes. Proceedings of the National Academy of Sciences, 103, 16349–16351.Google Scholar
Simmons, L. W., & Fitzpatrick, J. L. (2012). Sperm wars and the evolution of male fertility. Reproduction, 144, 519–534.Google Scholar
Simmons, L. W., Lüpold, S., & Fitzpatrick, J. L. (2017). Evolutionary trade-off between secondary sexual traits and ejaculates. Trends in Ecology & Evolution, 32, 964–976.Google Scholar
Simmons, L. W., Peters, M. P., & Rhodes, G. (2011). Low pitched voices are perceived as masculine and attractive but do they predict semen quality in men? PLoS One, 6, e29271.CrossRefGoogle ScholarPubMed
Smith, R. L. (1984). Human sperm competition. In Smith, R. L. (Ed.), Sperm competition and the evolution of animal mating systems (pp. 601–659). New York, NY: Academic Press.Google Scholar
Soini, P. (1987). Sociosexual behavior of a free‐ranging Cebuella pygmaea (Callitrichidae, platyrrhini) troop during postpartum estrus of its reproductive female. American Journal of Primatology, 13, 223–230.Google Scholar
Soler, C., Kekalainen, J., Nunez, M., Sancho, M., Alvarez, J. G., Nunez, J., … Gutierrez, R. (2014). Male facial attractiveness and masculinity may provide sex- and culture-independent cues to semen quality. Journal of Evolutionary Biology, 27, 1930–1938.Google Scholar
Somjee, U., Miller, C., Tatarnic, N. J., & Simmons, L. W. (2018). Experimental manipulation reveals a trade-off between weapons and testes. Journal of Evolutionary Biology, 31, 57–65.Google Scholar
Starratt, V. G., Goetz, A. T., Shackelford, T. K., McKibbin, W. F., & Stewart-Williams, S. (2008). Men’s partner-directed insults and sexual coercion in intimate relationships. Journal of Family Violence, 23, 315–323.Google Scholar
Starratt, V. G., McKibbin, W. F., & Shackelford, T. K. (2013). Experimental activation of anti-cuckoldry mechanisms responsive to female sexual infidelity. Personality and Individual Differences, 55, 59–62.Google Scholar
Tan, M., Jones, G., Zhu, G., Ye, J., Hong, T., Zhou, S., … Zhang, L. (2009). Fellatio by fruit bats prolongs copulation time. PLoS One, 4, e7595.Google Scholar
Thornhill, R. (2006). Forward: Human sperm competition and women’s dual sexuality. In Shackelford, T. K. & Pound, N. (Eds.), Sperm competition in humans: Classic and contemporary readings (pp. v–xix). New York, NY: Springer.Google Scholar
Ullman, S. E. (1999). A comparison of gang and individual rape incidents. Violence and Victims, 14, 123–133.Google Scholar
Voracek, M., Haubner, T., & Fisher, M. L. (2008). Recent decline in nonpaternity rates: A cross-temporal meta-analysis. Psychological Reports, 103, 799–811.CrossRefGoogle Scholar
Wedell, N., Gage, M. J., & Parker, G. A. (2002). Sperm competition, male prudence and sperm-limited females. Trends in Ecology & Evolution, 17, 313–320.Google Scholar
Wilson, N., Tubman, S. C., Eady, P. E., & Robertson, G. W. (1997). Female genotype affects male success in sperm competition. Proceedings of the Royal Society of London. Series B: Biological Sciences, 264, 1491–1495.Google Scholar
Wolf, M., Musch, J., Enczmann, J., & Fischer, J. (2012). Estimating the prevalence of nonpaternity in Germany. Human Nature, 23, 208–217.Google Scholar
Wood, K. (2005). Contextualizing group rape in post‐apartheid South Africa. Culture, Health & Sexuality, 7, 303–317.CrossRefGoogle ScholarPubMed
Wren, B. G. (1985). Handbook of obstetrics and gynaecology. London: Chapman & Hall.Google Scholar
Zavos, P. M. (1985). Seminal parameters of ejaculates collected from oligospermic and normospermic patients via masturbation and at intercourse with the use of a Silastic seminal fluid collection device. Fertility and Sterility, 44, 517–520.Google Scholar
Zavos, P. M., & Goodpasture, J. C. (1989). Clinical improvements of specific seminal deficiencies via intercourse with a seminal collection device versus masturbation. Fertility and Sterility, 51, 190–193.Google Scholar
Zemedkun, M. F. (2020). Cocktail parties and semen quality: Effects of auditory cues on semen parameters. Senior Independent Study Theses. Paper 9023.Google Scholar

Save book to Kindle

To save this book to your Kindle, first ensure coreplatform@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×