Female Copulatory Orgasm
Orgasm triggered by sexual intercourse.
KeywordsSexual Intercourse Mate Choice Sedative Property Female Orgasm Cryptic Female Choice
Emerging evidence suggests that orgasm elicited by sexual intercourse evolved to give women feedback about mate choice and to induce changes that increase the likelihood of impregnation.
Orgasm in men is nearly universal. However female orgasm is much more variable in frequency. Many theories have been advanced to explain the advantage that orgasm might confer in women. This entry examines recent evolutionary-based interpretations of female orgasm.
One of the leading interpretations of female orgasm is that because orgasm produces vaginal and intrauterine contraction it enhances sperm transport and retention, and it enables a woman who mates with multiple partners to selectively experience orgasm with the man with the best genes, thereby increasing the likelihood of conception and the corollary fitness of her offspring. This interpretation is supported by a study with undergraduate college students where female orgasm frequency and intensity were positively correlated with partner attractiveness (Gallup et al. 2014). Frequency of female orgasm was also correlated with partner family income level, suggesting a mechanism for identifying mate-provisioning ability. Additional support for this interpretation comes from a study where it was discovered that a woman’s likelihood of orgasm was positively correlated with how attractive the woman thought her partner was to other women (Sela et al. 2015).
There are other reasons to believe that orgasm increases the chance of impregnation. One study found that the experience of female orgasm increased the level of sperm retention after copulation for up to 8 days (Baker and Bellis 1993). Although this effect gradually declined with time, any orgasm which occurs afterward (including noncopulatory) served to reinstate and promote sperm retention. Additionally the amount of sperm retained from the first copulation was negatively correlated with the amount retained during a second copulation. It has been shown that oxytocin triggered by orgasm produces a dramatic increase in uterine peristaltic movements, which selectively propel sperm into the fallopian tubes (Wildt et al. 1998). Coupled with research which links levels of oxytocin with intensity of orgasm (Berlow 2004), it is reasonable to suppose that as orgasm intensity increases so should sperm transport and the likelihood of impregnation.
One of the biggest differences between male and female orgasm is the latter’s ability to experience multiple orgasms in a single encounter. The likelihood of experiencing multiple orgasms is positively correlated with female orgasm frequency and intensity, and the age of her partner (Gallup et al. 2014). Since the frequency and intensity of female orgasm is correlated with partner attractiveness and family income, this suggests that the experience of multiple orgasms functions as a signal that the woman has found a mate of significant fitness and provisioning potential. In addition, multiple orgasms may result in an even greater production of oxytocin thereby furthering the chances of conception.
Sedative Properties of Orgasm
Other adaptive features of female orgasm are its sedative properties. Females that experience sedative effects of orgasm are more likely to remain in a prone position for an extended period of time following insemination, and would benefit from reduced “flow-back” leading to increased sperm retention. The release of both oxytocin and dopamine in the brain during orgasm fall sharply afterward. This sudden surge and withdrawal of neurochemicals creates a feeling of being drained of energy; meanwhile as dopamine and oxytocin levels fall, prolactin levels rise which lead to feelings of satiation (Berlow 2004). Additionally prolactin increase following orgasm in females is four times greater after intercourse than masturbation (Brody and Kruger 2006). The sedative effect of orgasm is further implicated by a survey where 32 % of women reported the use of masturbation as an aide to help them fall asleep (Ellison 2000). The sedative effects of orgasm may play a role in mate choice by ensuring retention of the male’s sperm, prevention of further insemination by potentially lesser-quality males, and promotion of pair-bonding between the female and the high-quality male.
The role of orgasm during extra-pair copulations (EPC) may also serve to increase the likelihood of conception by the extra-pair (EP) male. Previous work has found that women are more likely to experience an orgasm and report orgasms of greater intensity during an EPC (Gallup et al. 2006); some research has even found that women are more likely to have multiple orgasms during EPCs. Baker and Bellis (1993) report that women who engaged in EPCs were more likely to retain the sperm of their EP mates and less likely to retain sperm from their committed partner (CP). This was due to the fact that orgasms were much more likely during an EPC, and that the number of noncoital orgasms increased after the EPC. The greater likelihood of orgasm during an EPC served to retain more sperm and the increase in noncoital orgasm frequency (largely as a consequence of masturbation) between the encounters serves to further promote retention of the EP sperm and block the CP sperm.
Lastly for a woman with a large number of children sired by her CP, each additional child becomes an increasingly redundant sample of the father’s genes. The reason for this is that the proportion of her partner’s genes not previously sampled is reduced by 50 % with each successive child. As a result, by the time a woman has three children sired by the same man she will have sampled on average 87.5 % of his genes. As a consequence conception as a result of an EPC/change in paternity would function to dramatically increase the range of genetic variance among her existing children, and genetic variation may be a hedge against an uncertain future.
Emerging evidence suggests that female orgasm functions to promote the movement of sperm up through the female reproductive tract and increase the likelihood of impregnation as a consequence. Research also suggests that female orgasms promote greater retention of sperm, and coupled with the sedative properties of orgasm women are more likely to remain in a prone position for an extended period of time following coitus which diminishes the loss of semen. There is also evidence that orgasms give women feedback about mate choice; i.e., females in committed relationships with an intelligent, healthy, high quality man are more likely to experience orgasm and their orgasms are also experienced as being more intense.
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