The Evolution of Sexuality by Todd K. Shackelford & Ranald D. Hansen

Author:Todd K. Shackelford & Ranald D. Hansen
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Conclusion

Symons (1979) argued that female orgasm is too difficult to induce, and its expression too variable among women, to be an adaptation. Lloyd (2005) echoed these sentiments: “very wide variability of rates of orgasm with intercourse suggests that there is no selection on female orgasm with intercourse. If there was, then we would expect a high, consistent expression of the trait of female orgasm with intercourse….” (p. 134). The reasoning is that if female orgasm is not reliably induced within and across women, then this challenges how efficiently and precisely it can perform any hypothetical function.

However, evidence reviewed above indicates that female orgasm may selectively promote conception with partners who possess specific orgasm-facilitating qualities. If so, then relatively difficult induction and relatively high variability in expression are expected. Because women are generally choosier than men over mates (Clark and Hatfield 1989; Schmitt 2005; Trivers 1972), a certain partner-specific contingency in orgasm induction is predicted by a mate choice hypothesis. This “choosiness” in orgasmic response should, and does (Lloyd 2005), apply especially to sexual intercourse, as opposed to less reproductively consequential behavior, such as masturbation. Much of the variation in orgasm frequency likely results from the facultative nature of orgasm—not all sexual stimulation is equal. Thus, women vary in orgasm frequency because they differ in the propitiousness of their mating circumstances, as well as in the response pattern relating those circumstances to their sexual responsiveness. Selection could reduce variation only in this response pattern. The relevant issue of how much orgasmic variation results from differences in women’s response patterns is presently unknown, but variability among women’s orgasm frequency per se does not warrant rejecting a functional hypothesis. In other words, the locus of selection and hence the focus of evolutionary analysis should be on the response pattern rather than the overall frequency. Moreover, even traits that have probably experienced strong selection, such as menstrual cycle length, stature, cognitive abilities, running speed, and facial attractiveness, are highly variable among individuals. Facultative adaptations (i.e. adaptations that are functional only in certain contexts) should exhibit even greater phenotypic variation (Hosken 2008; Puts 2007).

We may never be able to definitively state that female orgasm is an adaptation, as opposed to an exaptation or by-product . However, in the last several decades researchers have produced a great deal of evidence that has advanced our understanding of the phenomenon. Taken together, the data strongly suggest that female orgasm serves a reproductive purpose. Neither the phenomenology of female orgasm nor its underlying genital anatomy is vestigial, in contradiction with predictions of the by-product hypothesis. In fact, both female genital anatomy and the neural representation of orgasm in the brain are elaborated in some ways relative to homologous characteristics in the male, suggesting that female orgasm has been modified to serve a female-specific function. Neurological, endocrinological, and physiological studies suggest that female orgasm functions to increase the likelihood of conception. Oxytocin appears to play a dual role in orgasm, first facilitating its occurrence, then surging at the orgasmic peak

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