3. Penis size and female choice
One function of the penis is to provide sexual satisfaction to women (Mautz et al., 2013 Mautz, B. S., Wong, B. B. M., Peters, R. A., & Jennions, M. D. (2013). Penis size interacts with body shape and height to influence male attractiveness. Proceedings of the National Academy of Sciences, 110, 6925'6930.10.1073/pnas.1219361110[Crossref], [PubMed], [Web of Science '], [Google Scholar]). Masters and Johnson (1966 Masters, W. H., & Johnson, V. E. (1966). Human sexual response. Boston, MA: Little Brown. [Google Scholar], 1970 Masters, W. H., & Johnson, V. E. (1970). Human sexual inadequacy. Boston, MA: Little, Brown. [Google Scholar]) argued that the size of the penis plays little role in doing so. They reached this conclusion on the basis of their physiological studies that show that the vagina adapts to fit the size of the penis. Thus, they argued that any size penis will fit and provide adequate sexual stimulation to a woman. Nevertheless, subsequent studies indicated that size is important for the sexual satisfaction of women.
More specifically, in one study women were asked about the importance of two aspects of penis size: length and
Girth (Francken et al., 2002 Francken, A. B., van de Wiel, H. B., van Driel, M. F., & Weijmar Schultz, W. C. (2002). What importance do women attribute to the size of the penis? European
Urology, 42, 426'431.10.1016/S0302-2838(02)00396-2[Crossref], [PubMed], [Web of Science '], [Google Scholar]). About 21% rated length as important and about 33% rated
Girth as important. Another study asked 556 women aged 19'49 years about the importance of penis length and
Girth ('tulhofer, 2006 'tulhofer, A. (2006). How (un)important is penis size for women with heterosexual experience? Archives of Sexual Behavior, 35, 5'6.10.1007/s10508-006-8989-7[Crossref], [PubMed], [Web of Science '], [Google Scholar]). With respect to length, 57.4% considered it somewhat important, 18% very important, and 24.6% unimportant. With respect to
Girth, 53% considered it somewhat important, 21.5% very important, and 25.4% as unimportant. In addition, more experienced women judged penis size as more important, both in terms of length and
Girth. Similarly, one study in the Middle East found that women reported size to be important (67.2%), where 40% believed
Girth is most important and 40% valued both length and
Girth (Shaeer, Shaeer, & Shaeer, 2012 Shaeer, O., Shaeer, K., & Shaeer, E. (2012). The global online sexuality survey (GOSS): Female
Sexual Dysfunction among internet users in the reproductive age group in the middle east. The Journal of Sexual Medicine, 9, 411'424.10.1111/j.1743-6109.2011.02552.x[Crossref], [PubMed], [Web of Science '], [Google Scholar]). It was also found that dissatisfaction with a partner's penis size was associated with greater risk of female
Sexual Dysfunction.
In a different line of research, women from the USA, New Zealand, Cameroon, and China rated stylized male figures with somewhat longer than average penises as more attractive (Dixson, Dixson, Bishop, & Parish, 2010 Dixson, B. J., Dixson, A. F., Bishop, P. J., & Parish, A. (2010). Human physique and sexual attractiveness in men and women: A New Zealand'U.S. comparative study. Archives of Sexual Behavior, 39, 798'806.10.1007/s10508-008-9441-y[Crossref], [PubMed], [Web of Science '], [Google Scholar]; Dixson, Dixson, Li, & Anderson, 2007 Dixson, B. J., Dixson, A. F., Li, B., & Anderson, M. J. (2007). Studies of human physique and sexual attractiveness: Sexual preferences of men and women in China. American Journal of Human Biology, 19, 88'95.10.1002/(ISSN)1520-6300[Crossref], [PubMed], [Web of Science '], [Google Scholar]; Dixson, Dixson, Morgan, & Anderson, 2007 Dixson, B. J., Dixson, A. F., Morgan, B., & Anderson, M. J. (2007). Human Physique and sexual attractiveness: sexual preferences of men and women in Bakossiland, Cameroon. Archives of Sexual Behavior, 36, 369'375.10.1007/s10508-006-9093-8[Crossref], [PubMed], [Web of Science '], [Google Scholar]). Similarly, an Australian study of female assessment of digitally projected life-size, computer-generated images, found that women rated men with large penises as more attractive (Mautz et al., 2013 Mautz, B. S., Wong, B. B. M., Peters, R. A., & Jennions, M. D. (2013). Penis size interacts with body shape and height to influence male attractiveness. Proceedings of the National Academy of Sciences, 110, 6925'6930.10.1073/pnas.1219361110[Crossref], [PubMed], [Web of Science '], [Google Scholar]). In a representative Czech sample, 34% of the women with history of orgasm from penile'vaginal intercourse and enough coital partners to be able to make a comparison, reported being more likely to have an orgasm from penile'vaginal intercourse with a man who has a longer than average penis length (Brody & Weiss, 2010 Brody, S., & Weiss, P. (2010). Vaginal orgasm is associated with vaginal (not clitoral) sex education, focusing mental attention on vaginal sensations, intercourse duration, and a preference for a longer penis. The Journal of Sexual Medicine, 7, 2774'2781.10.1111/j.1743-6109.2009.01469.x[Crossref], [PubMed], [Web of Science '], [Google Scholar]). These results were also replicated in a Scottish sample (Costa, Miller, & Brody, 2012 Costa, R. M., Miller, G. F., & Brody, S. (2012). Women who prefer longer penises are more likely to have vaginal orgasms (but not clitoral orgasms): Implications for an evolutionary theory of vaginal orgasm. The Journal of Sexual Medicine, 9, 3079'3088.10.1111/j.1743-6109.2012.02917.x[Crossref], [PubMed], [Web of Science '], [Google Scholar]). An Internet study of 26,437 heterosexual female participants found that 94% of women who reported that their current partner's penis was 'large' were 'very satisfied' sexually, but only 32% of women whose partner's penis was 'small' were very satisfied sexually, and 68% of those women wished that their partner's penis was larger (Lever et al., 2006 Lever, J., Frederick, D. A., & Peplau, L. A. (2006). Does size matter? Men's and women's views on penis size across the lifespan. Psychology of Men & Masculinity, 7, 129'143.[Crossref], [Google Scholar]).
Evidence that female choice had been an important selection force operating on penis size has also been provided by a recent study (Apostolou, 2015a Apostolou, M. (2015a). Female choice and the evolution of penis size. Archives of Sexual Behavior, 44, 1749'1750.10.1007/s10508-015-0580-7[Crossref], [PubMed], [Web of Science '], [Google Scholar]). This study tested the hypothesis that, if in ancestral human societies female choice had been exercised on penis size, and given that women exhibit a stronger preference for
Girth than length (Eisenman, 2001 Eisenman, R. (2001). Penis size: Survey of female perceptions of sexual satisfaction. BMC Women's Health, 1, 1.10.1186/1472-6874-1-1[Crossref], [PubMed], [Google Scholar]; Francken et al., 2002 Francken, A. B., van de Wiel, H. B., van Driel, M. F., & Weijmar Schultz, W. C. (2002). What importance do women attribute to the size of the penis? European
Urology, 42, 426'431.10.1016/S0302-2838(02)00396-2[Crossref], [PubMed], [Web of Science '], [Google Scholar]), the observed penis size would be less variable in terms of
Girth than in terms of length. The reason is that female choice would have been stronger on
Girth than on length. Analysis of the variation in a large data-set found evidence which is consistent with this hypothesis.
Overall, as women are concerned about the size of their partners' penis, men who have alleles that predispose for sizes desirable to women will gain a selective advantage over men who have alleles which do not. In effect, understanding the variation that the size of the penis exhibits today, requires assessing the strength of female choice in ancestral human societies.