Evolution of female orgasm
Historically, in our society female sexuality has been neglected, to the point of proposing that female orgasm is a byproduct of male orgasm. On the contrary, studies in recent years have shown that orgasm is an important part of women's evolutionary strategy. Along with other disciplines, evolutionary psychology is helping to get out of the situation of ignorance, a fundamental phenomenon in women.
Evolution of female orgasm
Orgasm is a part of the sexual response where there is a strong sense of pleasure and an altered state of consciousness. In women it coincides with a muscular rhythmic contraction in the genital area and in men with ejaculation (Meston et al., 2004). Attached to the latter, orgasm is necessary for reproduction in men, but not in women. Based on this difference, Symons (1980) suggested that female orgasm would be an indirect product of the evolution of male orgasm. According to this hypothesis, female orgasm would have no function, but since women and men are very similar genetically and ontogenetically, women have that characteristic, as with men's nipples.
However, contrary to this hypothesis, in recent years there has been numerous evidence that female orgasm has an adaptive function. According to them, orgasm maximizes the reproductive success of women, that is, it is a phenomenon of maximizing the number of children that reach adulthood.
Female orgasm and copulation reinforcement
At the neurological level, dopaminated runoff in orgasm increases enormously with the activation of reward systems. This causes, in the short term, pleasure in orgasm and, in the medium-long term, the reinforcing effect. Thus, the individual motivates to repeat sexual behavior and to copulate again with the person who has experienced orgasm (Wheatley and Puts, 2015).
Although some studies have shown that women tend to experience orgasm because of intercourse less than men (García et al., 2014), further research has shown that the subjective experience of orgasm is very similar in men and women (Vance and Wgner, 1976) and that, in addition, women are more likely to have multiple orgasms (Masters and Johnson, 1966). This shows, as has been argued for men, that in women too orgasm would evolve as a motivating mechanism and increase the probability of fertilization in the medium term.
Female orgasm and fertilization
[Differences between species in ovulation by environmental effect (e.g.]. which occurs at a particular time of the year), may be due to the action of the male (through copulation) or be spontaneous. In species ovulated by a male, ovulation occurs by orgasm in females, in which case there is a direct relationship between orgasm and fertilization.
In humans, ovulation is spontaneous and is a process evolved from male induced ovulation (Pavlicev and Wagner, 2016). However, although orgasm in our species has lost the ability to induce ovulation, other physiological and physical changes associated with this type of ancient orgasm have been maintained that affect the probability of fertilization.
So in orgasm, the hormone oxytocin is secreted. This, in addition to promoting emotional attachment to the sexual partner (Levin, 2014), causes, as occurs in childbirth, muscle contractions of the vaginal and uterine walls. Vaginal contractions stimulate male ejaculation on the one hand and, on the other hand, facilitate the faster entry of sperm into the cervix, either directly (Levin, 2002) or because they invert the uterine pressure from the outside to the inside (Wildt et al., 1998; Lloyd, 2005). In addition to oxytocin, prolactin is secreted into orgasm, which facilitates sperm entry into the uterus, while enabling and activating sperm (Meston et al., 2004).
Therefore, female orgasm, although it does not produce the secretion of sexual cells as in male orgasm, has a series of effects that facilitate conception, which, together with the aforementioned motivating effect, highlights the adaptive function of this phenomenon.
Female orgasm, selection and partner retention
The differences between men and women in reproductive biology are remarkable, which has a direct impact on strategies to maximize the reproductive success of each sex. Men produce thousands of sperm a day, while women produce one egg, or several eggs, approximately every 28 days. On the other hand, because of menopause, the fertility of women is more limited than that of men, to which it should be added that women cannot re-fertilize during the nine months of pregnancy and lactation. It would therefore be possible for a man to have hundreds of daughters and sons, but that is impossible for women.
Thus, the most important factor that will limit the reproductive success of men will be sexual accessibility, while in women the survival of daughters will be greater. If we add to this that in the growth of the daughters female investment is very high (Pillswoth and Haselton, 2006) and that there may be health risks related to pregnancy and childbirth, it is easy to understand that the choice and adherence of a “bad” couple has more serious effects on women, so that women must be stricter than men when choosing a partner.
Although the original function of female orgasm has been to promote fertilization, in this context there is evidence that natural selection has led to a secondary process of adaptation of this phenomenon and that it has developed new functions related to partner selection and fixation (Gallup et al., 2018; Whatley and Puts, 2015).
Thus, it appears that female orgasm is related to the characteristics of sexual partners. For example, women have been shown to have more orgasms if their male sexual partners are more symmetrical (Thornhill, Gangestad, & Comer, 1995), more attractive (Puts et al., 2012; Shackelford et al., 2000), physically more masculine (Puts, Dawood, & Welling, 2012) and genetically more combinable at the level of complex central histocompatibility (Garver- Apgar et al., 2006). These characteristics have been related to men's health, fertility and good genes in general. However, it should be noted that this has only been observed in coital orgasm, which is obtained without peno-vaginal penetrations, does not influence these signs of partner. On the other hand, in species like ours, where the growth of offspring requires significant investment, the quality of the couple is not limited to beneficial genes, but can also be measured based on the availability and capacity to commit to the care and growth of the daughters. Gallup et al. (2014) found that the frequency and intensity of female orgasms was positively related to the personal safety of partners and family income. Other studies state that women's orgasm intensity is directly related to their satisfaction and emotional intimacy with their partner (Ellsworth and Bailey, 2013; King et al., 2011). More generally, it has been observed that women's sexual satisfaction is related to their partner's love and support (Gallup et al., 2014). This last idea explains, perhaps, why women get orgasm more easily by chewing or have sex with other women.
Together, these evidences suggest that for women orgasm can be an indicator of good quality of couples. Adding to this the reinforcing effect of orgasm and the facilitating effect of pregnancy, we observed that female orgasm favors pregnancy with higher quality men and, therefore, reproductive success of women. This effect is increased by the retention effects of the hormone oxytocin that secretes in orgasm.
Oxytocin favors positive communication, affiliation and emotional support among people, strengthening the mother-child relationship, but also the relationship with partner (Gangestad and Brege, 2017; Gallup, Towne, and Stolz, 2018). Thus, orgasm contributes to developing emotional closeness with the partner, which, as we have seen before, increases the likelihood of having orgasms with that partner in the short term and, in the medium-long term, increases the motivation to repeat sexual intercourse.
Moreover, the adaptive effects of female orgasm are not limited to heterosexual sex. In this sense, in our closest evolutionary relatives, bonobos (Pan paniscus), homosexual behaviors in females are frequent. Moreover, it has been observed that oxytocin secretion produced by orgasms related to these relationships increases cooperation between sexual partners (Moscovice et al., 2019), which is positively related to reproductive success, in primates, in the case of females, by the duration of the daughters of the fatherland (Silk et al., 2009). All this makes it clear, not only in terms of the evolution of female orgasm, but also of female homosexuality.
Finally, it is proposed that female orgasm acts as an “act that influences the behavior of others” (Wheatley and Puts, 2015). In favor of this idea, Ellswoth and Bailey (2013) found that the intensity of the external expression of orgasm of the woman (the incisos, the body expressions) positively predicts the satisfaction of man in the relationship and the motivation to invest in it.
In short, female orgasm, far from being a byproduct of male orgasm, is an evolved mechanism aimed at maximizing the reproductive success of women, thus shaping the evolution of our species. This is achieved through additional processes such as the more selective joining of couples with better genes and investment potential in the daughters of payroll, the increased likelihood of succession and the cooperation of sex members.
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