Of bugs and boojums: female orgasm as a facultative adaptation.

Wallen (2006, 2007) joins Lloyd (2005) in arguing that data on women’s orgasm frequencies contradict mate choice hypotheses for the evolution of female orgasm—and support the hypothesis that female orgasm is an evolutionary byproduct of male orgasm. I agree that female orgasm is not as reliable as male orgasm in the context of penile-vaginal intercourse, and that women’s reported orgasm frequencies are highly variable. But Wallen misrepresents these data, and both Wallen and Lloyd misinterpret them. Wallen and Lloyd cite evidence that women experience orgasms infrequently with penile-vaginal intercourse alone, compared to men and relative to masturbation or sex with manual or oral stimulation of the clitoris. Both take this as evidence that female orgasm is not well designed for consistent elicitation by penile-vaginal intercourse, and so is unlikely to be a mating-related adaptation. Wallen (2006) claims that ‘‘...less than 20% and possibly as few as 6% of women [achieve] orgasm from penile stimulation alone. The rest require additional direct clitoral stimulation manually, orally, or mechanically to achieve orgasm.’’ I cannot ascertain the source of the 6% figure, but Wallen (2007) attributes the 20% to Fisher (1973), who found that 20% of women reported never needing manual stimulation to achieve orgasm. According to Wallen, the other 80% of women require manual stimulation. By ‘‘require,’’ then, Wallen can only mean ‘‘sometimes require.’’ This is an odd meaning. If a woman more often has orgasms with manual stimulation but sometimes has them without, one might say that she does not require manual stimulation, though it helps. Regardless, Fisher (1973) found that 35% of women needed manual stimulation ‘‘50% or more of the time to attain orgasm’’ (p. 193). This means that 65% of women do not need manual stimulation 50% or more of the time. I wrote that, according to Fisher, ‘‘65% of women usually did not require manual stimulation of the clitoris to achieve copulatory orgasm’’ (Puts, 2006, p. 639). Wallen quotes me correctly, and then states that I ‘‘arrive at 65% [of women] never requiring manual stimulation for orgasm’’ (Wallen, 2007, my emphasis). To my mind, ‘‘usually did not’’ and ‘‘never’’ are different. Further, Wallen (2007) insists that this 65% figure is impossible because ‘‘60% of Fisher’s sample ‘more irregularly or not at all’ had orgasm in intercourse and 5–6% never had orgasm by any means.’’ Here, Wallen confuses two different questions: (1) Given a copulatory orgasm, how often is manual stimulation required? Fisher found that 65% of women required manual stimulation less than half of the time, and 20% never required it; (2) Given copulation, how often does orgasm occur? Fisher found that 60% had orgasm ‘‘more irregularly or not at all’’ (the only choice besides always or ‘‘nearly always’’). This confusion between data on the mode of copulatory orgasm and data on its frequency leads Wallen to believe that the data are contradictory, and that I must simply have ‘‘created’’ the 65% figure. Claiming that Fisher’s data were derived from only 85 women (the actual number is 285), Wallen suggests validating Fisher’s results with the larger sample of nearly 3,000 recruited by Dawood, Kirk, Bailey, Andrews, and Martin (2005). Wallen then mistakenly compares Dawood et al.’s data on the frequency of copulatory orgasm with Fisher’s data on its mode. Moreover, if Wallen was simply D. A. Puts (&) Neuroscience Program, Michigan State University, 108 Giltner Hall, East Lansing, MI 48824-1101, USA e-mail: [email protected]